Add per-key backlight off support and fix scroll lock indicator

[Lord-Memester]

Description

Added support for turning backlight off per-key.
Fixed typos.
Fixed implementation of scroll lock indicator.

Types of Changes

• Core
• Bugfix
• New feature
• Enhancement/optimization
• Keyboard (addition or update)
• Keymap/layout (addition or update)
• Documentation

Issues Fixed or Closed by This PR

Checklist

• My code follows the code style of this project: C, Python
• I have read the PR Checklist document and have made the appropriate changes.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• I have tested the changes and verified that they work and don't break anything (as well as I can manage).

[Lord-Memester]

Also notable:

In the main.js for the keychron web configurator tool, line 91171 is as follows:

                    return [w.r, w.g, w.b].some(m => m > 30) || (w[b] = Math.max(30, w[b])),

and performing a local override with the following minor change to that same line

                    return [w.r, w.g, w.b].some(m => m > 30) || (w[b] = Math.max(0, w[b])),

allows users to set hex #000000 for keys, which is what is required to disable them per-key.