Better compatibility with physical keyboard on Chromebook

### ⚠️ This issue respects the following points: ⚠️

- [X] This is a **enhancement/feature request**. Not a [bug or question](https://github.com/gsantner/markor/issues/new/choose).
- [X] The topic is **not** already reported at [Issues](https://github.com/gsantner/markor/issues?q=#js-issues-search). _(I've searched it)_.
- [X] Markor **is** up to date. See [Releases](https://github.com/gsantner/markor/tags) for the latest version. Updates are available from [F-Droid](https://f-droid.org/en/packages/net.gsantner.markor/) and GitHub.
- [X] The wanted feature/enhancement is not present in the latest code version (git master). (Please [download](https://nightly.link/gsantner/markor/workflows/build-android-project/master) and try the test version of Markor, named **Mordor**. Don't worry; Markor and Mordor appear as completely separate applications. You can install both side-by-side, and Markor's settings are not touched. If your desired feature is present, you don't need to open this issue. The change will be part of the next Markor update.)

### Description

1. Better keyboard compatibility with (Chromebook) physical keyboard

I am using a Lenovo Duet ChromeOS tablet. Markor works great with the touchscreen, but I notice that I cannot use my trackpad/cursor to click on toolbar buttons or insert (or remove) a tab character. Such functionality would be really useful to me. Any chance it's something you'd think about adding?

### Information

Android version: ChromeOS Version 105.0.5195.134
Device: Lenovo Duet 2-in-1 tablet
App Version: 2.10

### Source

Google Play

### Format / File type

Not specific

### Additional info / Log

```shell
-
```

Start by reproducing the reported behavior on a Lenovo Duet running ChromeOS with a physical keyboard, trackpad, and Markor 2.10. Investigate why the cursor cannot activate toolbar buttons or insert and remove tab characters. Done means those keyboard and pointing-device interactions work reliably in the editor.

Written by the indexing model from the issue text.