Add to Yeoman-x-VSCode

[BradTFT]

This pull request is centered around VSCode's extension building documentation.

Reasons to make this change

This gitignore file will contain all necessary files to ignore to increase the productivity of any project while using git to build an extension

documentation to the vscode extension building will be linked here: https://code.visualstudio.com/api/get-started/your-first-extension

(this is my first pull request sorry if i did something wrong or something)

[BradTFT]

could also be added to the file Yeoman.gitignore