Expand on documentation of available CSS properties.

Specify the fallback license for the sound effects.

I was prompted to do some digging to find this.
elementary though relicenses it under the Unlicense.

Populate changelog.

Merge remote-tracking branch 'contrib-ariana/issues'

Merge remote-tracking branch 'contrib-ariana/doc-update'

Added initial CSS API docs to CSS-Speech-Tutorial

- Adds new initial technical reference for the mentioned CSS properties.

  For example, usage of properties to vary voice articulation now
  include a full list of valid arguments, as well as a simple usage
  explanation.

- Adds new "**Wanted:**" tag to solicit further expansion on technical
  documentation.

- Adds new "**Wanted:**" tag to a few of the technical reference
  sections.

  I am not a proficient user of Haskell, and cannot discern a few of the
  valid keywords or syntax simply by reading through the code.

- Also makes a title more clear in CSS-Speech-Tutorial.md

Update & Fix grammar throughout docs files

Applies many small changes throughout the documentation files, aimed at
readability.

Added issue for discussing visual docs upgrades

- Adds initial launch point for discussion over visually enhancing the
  css-reference.html file.
  - Also suggests possible enhancements.

Added issue elaborating on lackluster audio licensing

ISSUES: Close play audio cues & arrow key nav

Added new issue to document forgotten CHANGELOG

Release Rhapsode2!

Add support for <form title>/<form alt>

Clarify installation instructions based on testing/feedback.

Improve fallbacks for missing markers.

Don't let marks interfer with silence collapsing.

Make '#' refer to top of page.

Draft SpeechD integration.

Implement table navigation.

Spanish useragent stylesheet localizations.