Timestamp, please

### ⚠️ 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 and checked most recent issues)_.
- [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 **Marder**. Don't worry; Markor and Marder 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

First of all, a great app. Kudos to the dev.
I'm looking more towards a journal with date and time. The Todo template adds dates to each entry (I love it), but I end up making more entries on the same day. While I don't use this template for my 'todo', I'd like to maintain a log with date and time for each entry I add. I'm not sure if there's a different template I should use or if I can tweak the Todo template. Please help.

### Information

Android version: 16
Device (phone model): Redmi note 15 5g
App Version: 2.16.1

### Source

GitHub Releases

### Format / File type

todo.txt

### Additional info / Log

```shell
-
```

No source file or test is named. Start by tracing the Todo template and todo.txt entry flow in the Android app, then clarify the desired timestamp format and insertion behavior. Done means repeated entries on the same day can be recorded with distinct date-and-time values.

Written by the indexing model from the issue text.