Improvements to documentation

[mjhopkins]

A bunch of minor improvements to the documentation.

Scala

• formatting
• fix ({double bracketing})
• write Quill uniformly (not quill). Likewise sbt not SBT
• spaces after commas and inside braces for improved legibility

English

• fix typos
• improve grammar

Notes

Additional notes.

Checklist

• Unit test all changes
• Update README.md if applicable
• Add [WIP] to the pull request title if it's work in progress
• Squash commits that aren't meaningful changes
• Run sbt scalariformFormat test:scalariformFormat to make sure that the source files are formatted

@getquill/maintainers

[mjhopkins]

At the moment I can't build this, because

curl "http://apache.volia.net/cassandra/$CASSANDRA_VERSION/apache-cassandra-$CASSANDRA_VERSION-bin.tar.gz"

refers to a path that does not exist on the host (CASSANDRA_VERSION=3.11.10).

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[guizmaii]

@mjhopkins These files have moved. Could you please backport your changes to the new files, please?

You'll also need to sign the ZIO cla before we can merge your PR