Add Save Button for Annotations

[BenShoeSpectric]

Is your feature request related to a problem? Please describe.
When making annotations I am unable to save annotations to the sigmf-meta file associated with the signal capture.

Describe the solution you'd like
I would like a function that lets me save the updated sigmf-meta data (annotations etc.) and keep it in the repository of signals without downloading, editing, and re-uploading the file.