Setup Dependabot & clean up build workflow

[TheRealPear]

• Added a Dependabot config file to scan through cargo and GA files to check and notify for any updates on a monthly basis.
• Changed build workflow to use Docker's recommended setup with matrices. This should come with less maintenance while keeping it mostly identical.
  • Based on discussion in the Discord, the only way to speed up ARM build is to just compile it locally or invest in a custom, actual ARM runner instead of using QEMU to emulate it.
  • (1/25/2025) GitHub has added linux arm64 runners, reducing the time down to 6 minutes. Naturally, Qemu is out and I reworked the matrices so it'll be easier to work with in the future.