docs: tidy up repository readme (#7889)

* remove reference to GitLab.com Renovte bot app

* capitalize word ESLint

* use American English spelling

* capitalize words Yarn, Lerna

* add missing dot at end of etc.

* remove dot from end of list item

* use one sentence per line

* fix list item spread out over lines

* capitalize word Yarn

* firm up recommendation

* rmeove extra word, fix grammar

* revert GitLab.com removal