Misc. visual enhancements for extension

[rvanbekkum]

Here are some suggestions for enhancements for the VSCode extension:

• The screenshots are not shown when you view the extension in the Visual Studio Marketplace or Visual Studio Code:

  

• The extension cannot be found that easily with the search function in VSCode. Maybe you can add some search keywords?

• The CHANGELOG is empty.

• The extension does not have a logo yet.

• The Repository link points to the GitHub repository of the code analyzer instead of the vsc-lintercop GitHub repository. It might be nice to change this and add a link in the README to point to the code analyzer repo.

• Might be nice to add badges to the README to indicate the installs and the LICENSE that applies. 😄

• Add the license property to the extension's package.json

[StefanMaron]

Keywords were already added, but it seems they just dont work.

The rest I tried to address :)