Add `.gitpod.yml` url extension validate

[mustard-mh]

Related Issues

Fixes https://github.com/gitpod-io/gitpod/issues/5466

How to Test

• Open Gitpod with current PR
• Open browser for port 9888
• Change .gitpod.yml vscode extension to something like below
• Check validator and quickfix
• ❓ How to find isMachineScoped extensions?

vscode:
  extensions:
    - dbaeumer.vscode-eslint
    - svelte.svelte-vscode
    - svelte.svelte-vscode-not-found12
    - https://openvsxorg.blob.core.windows.net/resources/redhat/java/linux-x64/1.13.2022112403/redhat.java-1.13.2022112403@linux-x64.vsix
    - https://openvsxorg.blob.core
    - https://openvsxorg.blob.core.windows.net/resources/timonwong/shellcheck/linux-x64/0.28.2/timonwong.shellcheck-0.28.2@linux-x64.vsix

Screenshot

URL not Installed

URL is not .vsix File

Quick Fix