Add official Discord link to Readme and docs

[nikosavola]

This PR adds a badge and a link to the official KQCircuits in the Readme and docs

Closes #40

[github-actions[bot]]

Test results

       6 files  ±0         6 suites  ±0   3m 39s :stopwatch: -18s    261 tests ±0     261 :heavy_check_mark: ±0  0 :zzz: ±0  0 :x: ±0  1 566 runs  ±0  1 566 :heavy_check_mark: ±0  0 :zzz: ±0  0 :x: ±0 

Results for commit 452b4ad6. ± Comparison against base commit 49daec4e.

[iqmtestd]

After some discussion we decided that we do not want to maintain permanent watch in a discord channel.