App can't insert or display tab characters properly

### Expected

When you press the Tab key on your keyboard, the app inserts and displays a tab.

### Observed

When you press the Tab key on your keyboard, the app instead moves the focus to the next field, which is the "tags" field at the bottom of the note.

Additionally, the app displays tab characters from pre-existing notes incorrectly. (The [web app](https://app.simplenote.com/) displays tabs as four spaces; the Android app displays tabs as one single space.)

### Notes

It would be excellent if you could please fix this bug.

Thank you for reading this, and for maintaining the app!

I suspect this bug is reproducible on all Android devices. My device is described below.

Device Make: LG
Device Model: G5
Android Version: 8 "Oreo"
Simplenote Version: 2.23

Start by reproducing the issue in the Android note editor, including pressing Tab and opening a pre-existing note containing tabs; the issue identifies the tags field as the focus destination. Trace the note editor's focus handling and tab rendering, then verify that Tab remains in the note and existing tabs display consistently.

Written by the indexing model from the issue text.