docs(performance): added highlight article for improved concurrency (#10469)

* added highlight article for improved concurrency and fixed a very minor typo in implicit namespacing article

* Update website/content/en/highlights/2021-12-14-improved-concurrency-model.md

Co-authored-by: Jesse Szwedko <jesse@szwedko.me>

* addressed jesse and luke's comments

* removed a trailing space

* Revisions

Signed-off-by: Jesse Szwedko <jesse@szwedko.me>

Co-authored-by: Jesse Szwedko <jesse@szwedko.me>