Enhancement: Add release binaries for MIPS architectures

We've added a few new architectures for Linux to the release binaries: `mips`,
`mipsle`, `mips64`, and `mip64le`. MIPS is mostly used for low-end embedded
systems.

https://github.com/restic/restic/issues/3191
https://github.com/restic/restic/pull/3208
