Expand dsmr_reader documentation

[Glodenox]

Proposed change

Add more information on how the sensors in DSMR Reader are best used within the Energy Dashboard. Quite a few people were having issues with this (mostly due to the changes in the state class of some entities).

Additionally, I've better clarified the difference with the DSMR integration. I'm not sure why I previously stated that it provides an instance of DSMR Reader directly, as it has nothing to do with DSMR Reader at all.

Type of change

• Spelling, grammar or other readability improvements (current branch).
• Adjusted missing or incorrect information in the current documentation (current branch).
• Added documentation for a new integration I'm adding to Home Assistant (next branch).
  • I've opened up a PR to add logo's and icons in Brands repository.
• Added documentation for a new feature I'm adding to Home Assistant (next branch).
• Removed stale or deprecated documentation.

Additional information

No other information

Checklist

• This PR uses the correct branch, based on one of the following:
  • I made a change to the existing documentation and used the current branch.
  • I made a change that is related to an upcoming version of Home Assistant and used the next branch.
• The documentation follows the Home Assistant documentation standards.

[frenck]

Thanks, @Glodenox 👍

../Frenck