Add basic splitting / cut-out / delete functionality

[elishamint]

In conjunction with issue #6 (add marker/bookmark feature) it should be rather simple to also make it able to split files at marker positions, and delete portions between markers. A feature that could make this app stand out from all the other similar ones.

I came here looking for an application for Android that provides this basic functionality but none of the dozen recorders I've seen has this. The only way for me to do this rn is by using ffmpeg directly (ffmpeg GUI for Android is available). That's tedious though, if the purpose is to quickly cut out the significant portions from a voice note or session recording.

[Maxitendo1]

@elishamint SimpleMobileTools apps were sold to ad and spyware company. Fork is here:

https://github.com/FossifyOrg