Add VSCodium, the freely-licensed binary distribution of Visual Studio Code

[jvasseur]

Add VSCodium which is distribution of VSCode without the telemetry and non-open-source stuff included in the standard distribution of VSCode.

The watch file and template are mostly the sames as the ones for VSCode except with adapted URLs.

The vs-codium.xml file is juste the result of 0watch picking up the last 30 releases, since this is a tool were people are less likely to want to install an older version I don't think we need to include all the versions but adding the last 30 will prevent 0watch to try to add them (the github API returns 30 releases by default).

[bastianeicher]

Thanks for the contribution!

Would you mind creating an additional MR for the gh-pages branch that adds the .png, .ico and .icns files? The signed .xml will automatically be placed in that branch by CI once this PR is merged, but the icons need to be added once manually.

[jvasseur]

Here is the PR for the icons: #1166.

I did wonder how the icons were managed since I didn't see any icons it the repo, didn't think to check on another branch.