Add a built-in guitar Tuner

I am a beginner guitarist. Soundbrenner is very useful. It would be really more helpful to have a guitar tuner built right into the app. That way, users could tune their instruments quickly without needing to switch to a separate app or use an external tuner. The tuner could have both automatic mode (using the phone’s microphone to detect the pitch) and manual mode (playing the standard tuning notes: E, A, D, G, B, e). It’d be great to include a simple visual guide—like a needle or colored indicators—to show when a string is in tune. Bonus points if it supports alternate tunings like Drop D or DADGAD. Ideally, it could be placed somewhere easy to find—like on the home screen or in a “Tools” or “Tuner” tab—so users can quickly tune up before playing or practicing. Let me know if you want it shorter, more casual, or more formal!

Merged into "App: add tuner feature (Android)" #242

Hey, this already exists on iOS :) Will definitely bring this to Android as well at some point