Fixes #3268

Summary

• Various style and grammar updates, including the following:

  • Avoid ellipses (reference)
  • Hyphen vs. em dash (reference)
  • Key-value, not “key -> value” (reference)
  • Headings should be sentence case (reference)
  • Use the serial comma (reference)
  • Use parentheticals only when needed (reference)
  • No exclamation points (reference)
  • Use negation contractions (reference)
  • Don't capitalize feature names like dictionary (reference)
  • Consistency fixes: New York City/NYC, primary key/primary index, compute/calculate, switching between first and second person for the audience (it should always be second)

• Remove "marketing lingo"

  • Superlative language like "blazing fast", "amazing collection", or "the s3 cleverly knows" doesn't fit with the purpose or tone of product documentation.
  • Product docs should be clear, concise, and focused on showing them how to do the task at hand.

• Organization and user experience

  • Don't number h2s.
  • Collapsed expected output code blocks for queries section to make it more scrollable.
  • Including dictionaries link in-line instead of telling user to scroll to the bottom.
  • Link to existing description for LIFETIME instead of trying to reinvent the wheel here.
  • Use note formatting sparingly to avoid fagtigue.
  • Final section was randomly h4 nested under the Perform a join section.

• Example says "right join" but code shows inner join