Documentation of new modules

[fel115]

Create documentation in the doc folder for the new modules:

• [x] audio.rs
• [x] bat.rs (Capacity)
• [x] nextcloud.rs (Commands)
• [x] ping.rs
• [x] signals.rs
• [x] types.rs

and then remove:

• [x] doc/modules.md

[markus2330]

I added

"and then remove doc/modules.md"

above.

[markus2330]

@fel115 can you please merge the content of https://github.com/ElektraInitiative/PermaplanT/pull/956 and doc/modules.md into the proper places in doc/<module>?

[fel115]

What does the PermaplanT PR do? Adding a guide?

[markus2330]

Sorry, wrong link (copy&paste error), I mean #77 etc.

[fel115]

See PR #115

[markus2330]

Great, except of what is written in #101 it is a good start for the module documentation.