Integrate with the VSCode tasks API to provide easy ways to run/build/verify/test a Dafny project

[keyboardDrummer]

VSCode has APIs for making it easier to run CLI tools that operate on code being edited in VSCode. This extension should use those APIs.

From the VSCode docs on tasks: https://code.visualstudio.com/docs/editor/tasks

Lots of tools exist to automate tasks like linting, building, packaging, testing, or deploying software systems. Examples include the TypeScript Compiler, linters like ESLint and TSLint as well as build systems like Make, Ant, Gulp, Jake, Rake, and MSBuild.

These tools are mostly run from the command line and automate jobs inside and outside the inner software development loop (edit, compile, test, and debug). Given their importance in the development life cycle, it is helpful to be able to run tools and analyze their results from within VS Code. Tasks in VS Code can be configured to run scripts and start processes so that many of these existing tools can be used from within VS Code without having to enter a command line or write new code. Workspace or folder specific tasks are configured from the tasks.json file in the .vscode folder for a workspace.

https://code.visualstudio.com/api/references/contribution-points#contributes.taskDefinitions

https://code.visualstudio.com/api/extension-guides/task-provider