Rewrite Readme

[Confectrician]

Readme has to be adapted to the current changes.

Todo's:

• [x] Changed folder structure
• [x] Build/Pipeline environment
• [x] Webpack config and usage
• [x] Build workaround for client/node_modules/copy-paste/index.js -> Lines 34-36 (openbsd)
• [x] New gifs/screenshots since we have many wrong informations in the existing ones
• [x] Activation events

[Confectrician]

I had some detail look at the Readme and i think it will blew up the file with those additional informations.

Many of them are related to development and should not be shown in the marketplace description, which is based on the repositories Readme file.

For now i will put this niformatoin in the Contributing file, bit this one is filled with much information too already.

[Confectrician]

I will leave out activation events, since the documentation on https://code.visualstudio.com/api is very clear about that.