Feature: App crash handler / Log export

### ⚠️ 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 development 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

Application crashes happen wanted or not. Often users don't attach logfiles (in sense of `adb logcat`) to issues, which would make fixing the issue and finding out why it happens a lot easier.

So for that reason it would be great to have a crash handler at Markor, that after a crash pops up (i.e. a dialog), showing the stacktrace. Also a copy to clipboard /share to button is good to have, so users can export the log to i.e. upload it i.e. on GitHub or send by mail or something.

One way to go for this seems to be a `Thread.UncaughtExceptionHandler`, here is some information:

As of whats not wanted:
* Preferably no additional dependency/library, looks like it can be done without too much on own.
* No upload, "call home", analytics, tracking features. The crash should be inspectable by user, and they should decide on their own what todo with the information

### Information

Android version: Any
Device: Any
App Version: 2.10.5

### Source

git master branch

### Format / File type

Not specific

### Additional info / Log

```shell
-
```

Start by investigating Android's Thread.UncaughtExceptionHandler and the adb logcat information described in the issue. Determine how Markor could present a post-crash stack trace with copy and share actions while avoiding extra dependencies, uploads, analytics, or tracking. Done means users can inspect the crash and choose whether to export it.

Written by the indexing model from the issue text.