docs(guide/expression): update diff list between JavaScript and Angular expressions

add paragraphs about function declaration, comma and void operators and
RegExp to the diff list in the beginning of articule

Closes #10418
Closes #10452
docs(tutorial/index): improve capitalization

Improve capitalization in acronyms for better clarity.
docs(angular.identity): add @param and @returns tags

Closes #10457
docs(guide/E2E Testing): add '-' to 'end-to-end'

Closes #10458
docs(guide/Scopes): fix capitalization

This sentence should begin with a capital 'R', not a lower case one.

Closes #10472
docs(error/badcfg): add missing "but"

Sentence meaning was unclear; added what I assumed should have been a "but"

Closes #10473