docs(guide/accessibility): Add in-depth guide

Closes #9930
docs(guide,tutorial): fix outdated Protractor API link

Link to the gh-pages deployment of protractor docs, it's much easier on the eyes.

Closes #9946
docs(guide/concepts): spell "Angular" with cap "A", fix typos

In these two instances, Angular was spelled with a lower-case "a." All occurrences should be spelled
consistently.

Compound adjectives preceding the noun they modify should generally be hyphenated (cf Chicago Manual
of Style, 6.40), e.g., "so-called directives."

Closes #9896
docs(CHANGELOG): Document breaking change from 23bc92b1

Document the breaking change from 23bc92b1

Closes #9947