Automate releases via Github Actions

[Gusted]

• Use Github Actions to compile static linked binaries for the three major OS and upload them to Github Releases.
• You would need to configure a GITHUB_TOKEN secret within https://github.com/mCaptcha/mCaptcha/settings/environments

[realaravinth]

I'm unfamiliar with publishing binaries, also I've faced issues when trying to cross-compile OpenSSL(a dependency(sqlx) uses it).

I'll merge it now, but I'll come back to it should it break. :)