docs: Add GNSS Master app details to smartphone-rover-apps.md

[TKuzmenko-EPS]

Added a new section for the GNSS Master app, detailing its features and functionalities for GNSS/RTK receivers.

[y3nd]

Thanks for the PR!
Please make the edits for the french version too.
May I know why you converted the image to jpg? Avif allows better compression and is widely supported.
Also, the image asset is missing.

[TKuzmenko-EPS]

Hello! I represent ArduSimple. We were in touch with Philippe Bourcier, who advised us to edit these specific pages.
Could you also share the French version?
Philippe also suggested to use JPG instead of Avif.
i was not able to add the file as i do not have permissions so i send it to Philippe.
Please advice the

best way to proceed