Creating a new visual studio code extension

Project start

Install yo npm package
npm i -g yo

Now go to your project folder and genearte template using yo
Open command prompt
yo code

Building the extension

Make sure that you have publisher names and other requirement information in the package.json file

Make sure that you edit Readme.md file

"categories": [
        "Other",
        "Snippets"
    ],
    "keywords": [
        "flutter",
        "keywords01",
        "keywords02"
      ],

    "publisher": "yourname",
    "icon": "local/path/to/icon",
    "author": {
        "email": "youremail@gmail.com",
        "name": "Your name",
        "url": "Your github page"
    },
    "license": "MIT",
    "contributors": [
        {
        "name": "Other contributer",
        "email": "email@gmail.com",
        "url": "contributer_github_page"
        }
    ],
    "repository": {
        "url": "repository url of the package"
    },

Open cmd windows in your root project folder

vsce package

Publishing 

Go to visual studio marketplace
https://marketplace.visualstudio.com/VSCode

Login with your microsoft account

And create a new plugin there and submit!