FEAT: add the option to target specific file rather than README.md

[fbuireu]

Is your feature request related to a problem? Please describe. By default (as it should be) it uploads automatically the README.md file. I imagine some other scenarios where someone may want to update another file (let's say README_it.md beside the activity will be displayed in English).

Describe the solution you'd like I'd like the option to use different markdown files to be uploaded using a key like: TARGET_FILE.

Describe alternatives you've considered I'll try to make a PR if my free time allows me.

Thanks for all the work!

[fbuireu]

Is there any improvement or resolution about that?

[frontendreleases]

It will be extremely helpful and cool. I'm looking forward this too!

[fbuireu]

Is this project still maintained by the author? I would like to see what's going or if I need to switch to another active project