Repository navigation

docs: reorganize references, and restructure Plugins into Add-ons (#315) #1056

Job	Run time
e2e	2m 51s
unit-test / test (ubuntu-latest, 24)	2m 59s
unit-test / test (ubuntu-latest, 26)	2m 52s
unit-test / lint	4m 33s
unit-test / test (windows-latest, 24)	4m 21s
unit-test / test (windows-latest, 22)	4m 56s
unit-test / test (ubuntu-latest, 22)	2m 57s
unit-test / test (windows-latest, 26)	4m 7s
	29m 36s