Add support for Vector2/3/4, Quaternion, Rect; expand support for RGB-only Color

[kaycodes13]

Summary of Changes

Closes #78 by:

• Adding a set of TextModels utilities to create models for Vector2, Vector3, Vector4, Quaternion, and Rect types.
• Adding custom input validation for those types to TextInput.
• Adding a set of methods for generating elements for those types in ConfigEntryFactory and MenuProperty.

Other updates folded into this:

• Added an RGBElementFactory for source generation of color inputs that mirrors the effect that RGBColorValues has for config entry element generation.
• Added an underline to text fields, because I think it's a little confusing to encounter an empty text field without any visual indication that there's a spot to type something.

Checklist

• No change is too small for a release, so pick one:
  • I have updated the package version following semantic versioning
  • There is another change actively WIP that will update the version (link issue or PR here)
  • This PR does not update user-facing code/config
  • I'm not sure how to set the version and would like the reviewer's help

[dplochcoder]

Mostly LG, just a couple comments left + Flib's comment about the RGB attribute

[flibber-hk]

How wedded are you to this underline? I think it looked better without the underline, personally

(To be clear, I don't mean we should keep - or remove - it based solely on my opinion, but I'd like it to be scrutinized further)

[flibber-hk]

I think this is a case where bumping the version should be done outside the PRs - the other PR has breaking changes so the version should be 0.8 rather than 0.7.5, but it's weird to bump the version here based on the changes in the other PR. I don't think we should create a release with the other PR without this one being included - can you remove the version update from this PR and (if you want to) add it to the other PR?