doc: fix

Author: pollenjp

README.md

@@ -27,7 +27,7 @@ While Ansible's `playbook` and `inventory` files are written in YAML format, man
 cargo binstall cdk-ansible-cli
 ```
 
-### Shell
+### shell
 
 See [the latest release page](https://github.com/pollenjp/cdk-ansible/releases/latest) and run the command like below.
 
@@ -108,7 +108,7 @@ cd cdk-ansible
 cargo run --package your-app -- synth --output-dir ../ansible
 ```
 
-```txt
+```text
 proj-root/
 |-- cdk-ansible/
 `-- ansible/              ... Your ansible project