Signal-android: Publicly available APK

[hiredgunhouse]

Please make APK publicly available for those who do not want to sign-up to Google services like Play store.
I suppose GitHub releases feature would be perfectly fine, ideally you could put the APK on F-Droid.

[2-4601]

Please read the guidelines for contributing article that's visible when you open a new issue. Also please read the issue template and search for existing issues before opening new ones.
Closing as duplicate of #122, #127, #281, #282, #458, #525, #722, #2858, #3435, #3954, #4429, #4430.

[hiredgunhouse]

@2-4601 I did search for existing issues but missed the one at the bottom of the page, my bad. As for the template I did not bother to read it cause I figured it is for bugs not requests and turns out I was right.

[Nhorning]

Just to point out on this - Signal is now recommended by Security in a Box, so our org is doing trainings on it for Human Rights defenders. Having 25 people download the app from the play store using the wifi of a venue in a less developed country is a bit impractical.