Add CI for shaderc.zig

[tiawl]

• [x] Add a workflow to clone users and test the new release
• [x] Add a cron workflow to fetch dependencies and make pull request
• [x] Merge this: https://github.com/tiawl/spirv.zig/pull/1
• [x] Merge this: https://github.com/tiawl/glslang.zig/pull/2
• [x] Add update label
• [x] Change general settings to allow github actions to make PR
• [x] Run bot
• [x] Merge bot PR if any
• [x] Add protection rule for default branch
• [x] Add it to CI toolbox workflow
• [x] Add it to protection rule of toolbox default branch

[tiawl]

Available here:

• https://github.com/tiawl/shaderc.zig/blob/trunk/.github/workflows/bot.yml
• https://github.com/tiawl/shaderc.zig/blob/trunk/.github/workflows/ci.yml