ggml : add version function to get lib version (#1286)

ggml : add version function to get lib version (#1286)

* ggml : add version function to get lib version

This commit adds a function `ggml_version()` to the ggml library that
returns the version of the library as a string.

The motivation for this is that it can be useful to be able to
programmatically check the version of the ggml library being used.

Usage:
```c
printf("GGML version: %s\n", ggml_version());
```
Output:
```console
GGML version: 0.0.2219
```

* ggml : add ggml_commit()

---------

Co-authored-by: Georgi Gerganov <redacted>