add riscv64 support

[mengzhuo]

Act version

act version 0.2.63-1-g71a6fa0

Feature description

I had successfully built and run on riscv64 (bpi-f3)
Can we add riscv64 to prebuilt binary? I can send a PR if possible.
Thanks.

# act --version
act version 0.2.63-1-g71a6fa0
# go version `which act`
/usr/local/bin/act: go1.21.1
# uname -a
Linux bpi-f3-1 6.1.15 #1.0~rc1 SMP PREEMPT Mon Apr 29 09:05:59 UTC 2024 riscv64 riscv64 riscv64 GNU/Linux

[ChristopherHX]

I can send a PR if possible

If you create a PR, we can probably add it.. I would approve such a change to the goreleaser files.

My downstream project includes that target for some years, recently even loong64....
See here for technically possible list act targets (some of them have problems with the cli frontent) https://github.com/ChristopherHX/github-act-runner/releases