talkatu/talkatu

Migrate to gi-docgen and remove the doc comments that were gtk-doc specific

Testing Done:
Build the docs locally and via the convey plan.

Reviewed at https://reviews.imfreedom.org/r/1056/
# Building
Talkatu uses [meson](https://mesonbuild.com) as it's build system.
Meson requires you to build in a directory other than the source directory.
To compile you can use the following commands:
```
meson build
cd build
ninja install
```