add prompt template tool and flow

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docs/how-to-guides/develop-a-tool/add-prompt-template.md

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+# Add prompt template
+Users sometimes need to use prompt template within their tools. To simplify this, we've introduced the `PromptTemplate` feature.  
+In this guide, we will provide a detailed walkthrough on how to use `PromptTemplate` as a tool input. We will also demonstrate the user experience when utilizing this type of tool within a flow.
+
+## Prerequisites
+Follow the [steps](create-and-use-tool-package.md#Prerequisites) to prepare prerequisites.
+
+## How to create a tool with prompt template
+Here we use [an existing tool package](../../../examples/tools/tool-package-quickstart/my_tool_package) as an example. If you want to create your own tool, please refer to create and use tool package.
+
+1. Add a `PromptTemplate` input for your tool, such as in [this example](../../../examples/tools/tool-package-quickstart/my_tool_package/tools/tool_with_prompt_template_input.py)
+
+    ```python
+    from jinja2 import Template
+    from promptflow import tool
+    from promptflow.connections import CustomConnection
+    # 1. import the PromptTemplate type
+    from promptflow.contracts.types import PromptTemplate
+
+
+    # 2. add a PromptTemplate input for your tool method
+    @tool
+    def my_tool(connection: CustomConnection, prompt: PromptTemplate, **kwargs) -> str:
+        # 3. customise your own code to handle and use the prompt here
+        message = Template(prompt, trim_blocks=True, keep_trailing_newline=True).render(**kwargs)
+        return message
+    ```
+
+2. Configure the tool YAML, Note that the `PromptTemplate` input should not be included in the YAML, like in [this example](../../../examples/tools/tool-package-quickstart/my_tool_package/yamls/tool_with_prompt_template_input.yaml)
+
+    ```yaml
+    my_tool_package.tools.tool_with_prompt_template_input.my_tool:
+    name: Tool with PromptTemplate
+    description: This is a tool to demonstrate the usage of PromptTemplate
+    type: custom_llm
+    module: my_tool_package.tools.tool_with_prompt_template_input
+    function: my_tool
+    inputs:
+        connection:
+        type:
+            - CustomConnection
+    ```
+
+## Use tool with a prompt template input in VS Code extension
+Follow steps to [build and install your tool package](create-and-use-tool-package.md#build-and-share-the-tool-package) and [use your tool from VS Code extension](create-and-use-tool-package.md#use-your-tool-from-vscode-extension).
+
+Here we use an existing flow to demonstrate the experience, open [this flow](../../../examples/flows/standard/prompt-template-input-tool-showcase/flow.dag.yaml) in VS Code extension
+- There is a node named "tool_with_prompt_template" with prompt template file, and the inputs of this node contains the input for the prompt template..
+
+![use_prompt_template_in_flow](../../media/how-to-guides/develop-a-tool/use_prompt_template_in_flow.png)

examples/flows/standard/prompt-template-input-tool-showcase/flow.dag.yaml

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+inputs:
+  text:
+    type: string
+    default: Microsoft
+outputs:
+  output:
+    type: string
+    reference: ${tool_with_prompt_template.output}
+nodes:
+- name: tool_with_prompt_template
+  type: custom_llm
+  source:
+    type: package_with_prompt
+    tool: my_tool_package.tools.tool_with_prompt_template_input.my_tool
+    path: prompt_template.jinja2
+  inputs:
+    connection: open_source_llm
+    text: ${inputs.text}

examples/flows/standard/prompt-template-input-tool-showcase/prompt_template.jinja2

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+Hello {{text}}.

examples/flows/standard/prompt-template-input-tool-showcase/requirements.txt

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+promptflow
+promptflow-tools
+my-tools-package

examples/tools/tool-package-quickstart/my_tool_package/tools/tool_with_prompt_template_input.py

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+from jinja2 import Template
+from promptflow import tool
+from promptflow.connections import CustomConnection
+from promptflow.contracts.types import PromptTemplate
+
+
+@tool
+def my_tool(connection: CustomConnection, prompt: PromptTemplate, **kwargs) -> str:
+    # Replace with your tool code.
+    # Usually connection contains configs to connect to an API.
+    # Use CustomConnection is a dict. You can use it like: connection.api_key, connection.api_base
+    # Not all tools need a connection. You can remove it if you don't need it.
+    message = Template(prompt, trim_blocks=True, keep_trailing_newline=True).render(**kwargs)
+    return message

examples/tools/tool-package-quickstart/my_tool_package/yamls/tool_with_prompt_template_input.yaml

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+my_tool_package.tools.tool_with_prompt_template_input.my_tool:
+  name: Tool with PromptTemplate
+  description: This is a tool to demonstrate the usage of PromptTemplate
+  type: custom_llm
+  module: my_tool_package.tools.tool_with_prompt_template_input
+  function: my_tool
+  inputs:
+    connection:
+      type:
+        - CustomConnection