Refactor Gitpod configuration to improve quick spin up of automated dev environments (#21411)

This commit instructs Gitpod to run `docs` in watch mode in fresh
development environments so any dev could start hacking in seconds.

Also included some vscode extensions for Vue, Go, and Docker.


Try it here:

[![Open in
Gitpod](https://gitpod.io/button/open-in-gitpod.svg)](https://gitpod.io/#https://github.com/yardenshoham/gitea/tree/gitpod)

Signed-off-by: Yarden Shoham <hrsi88@gmail.com>
Co-authored-by: Gusted <williamzijl7@hotmail.com>

docs/content/doc/developers/hacking-on-gitea.en-us.md

@@ -19,6 +19,12 @@ menu:
 
 {{< toc >}}
 
+## Quickstart
+
+To get a quick working development environment you could use Gitpod.
+
+[![Open in Gitpod](https://gitpod.io/button/open-in-gitpod.svg)](https://gitpod.io/#https://github.com/go-gitea/gitea)
+
 ## Installing go
 
 You should [install go](https://golang.org/doc/install) and set up your go