Improve Lua code to get current version

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### How are you using the lua-language-server?

NeoVim

### Which OS are you using?

Other

### What is the issue affecting?

Other

### Expected Behaviour

I would like to get the current version for lua-language-server without `changelog.md` file.

Improve Lua code in `script/version.lua` to get current version (last Git tag).

### Actual Behaviour

When a contributor packages lua-language-server for a distribution (Linux or BSD), the `changelog.md` file is not always included.

In `script/version.lua` file, the current version is defined (function `loadVersion`) with parsing of the `changelog.md` file. **If this file is not present, the returned version is `Unknown`**.

It will be better to get the current version without parsing of `changelog.md` file => get version from the last Git tag or define the current version in `script/version.lua` file.

### Reproduction steps

N/A

### Additional Notes

_No response_

### Log File

_No response_

Beginne in script/version.lua bei loadVersion und untersuche, wie die aktuelle Version aus changelog.md abgeleitet wird. Reproduziere den Packaging-Fall, in dem changelog.md fehlt, und überprüfe anschließend, dass die Version aus dem letzten Git-Tag oder einem explizit definierten Wert stammt, statt Unknown zurückzugeben.

Vom Indexierungsmodell aus dem Issue-Text verfasst.