feat: find web browser via flatpak portals

[williamjmorenor]

Hello

I am playing with the packaging as flatpak of app using flaskwebgui to serve a flask app as desktop app.

By default apps running as flatpak have very limited access to the host system.

To have access to the host system you must provide --filesystem=host-os:ro to access the /usr/bin dir that become available under /run/host/usr

The proposed changes include these dir to find a web brower after looking at a system installed one.

I certify that the proposed changes are my authorship and I agree that they will be included in the source code of the application under the terms of the project license.

[ClimenteA]

When finding a browser for linux this line: subprocess.check_output(["which", os.path.basename(path)]) - should take care of all the possible paths that are not provided, but adding a few paths won't break anything.

Some updates:

• Bump version to version="1.1.2" in setup.py;
• Include some docs on how to package/publish the app using flatpack in the Distribution section of the readme file;
• Minimize comments - one line comment should be enough (Web browsers installed via flatpack);
• (Optional) Maybe research how to package/publish it under snap?

[williamjmorenor]

for any looking for this in the future (hopes search index will find this):

Example of packaging a flaskwebgui powered app as flatpak: https://github.com/cacao-accounting/cacao-accounting-flatpak

Example of packaging a flaskwebgui powered app as snap: https://github.com/cacao-accounting/cacao-accounting-snap

[ClimenteA]

Nice man!