RFR: 8301121: RichTextArea Control (Incubator)

[Andy Goryachev]

Incubating a new feature - rich text control, **RichTextArea**, intended to bridge the functional gap with Swing and its StyledEditorKit/JEditorPane. The main design goal is to provide a control that is complete enough to be useful out-of-the box, as well as open to extension by the application developers.

This is a complex feature with a large API surface that would be nearly impossible to get right the first time, even after an extensive review. We are, therefore, introducing this in an incubating module, **jfx.incubator.richtext**. This will allow us to evolve the API in future releases without the strict compatibility constraints that other JavaFX modules have.

Please check out two manual test applications - one for RichTextArea (**RichTextAreaDemoApp**) and one for the CodeArea (**CodeAreaDemoApp**). Also, a small example provides a standalone rich text editor, see **RichEditorDemoApp**.

**References**

- Proposal: https://github.com/andy-goryachev-oracle/Test/blob/main/doc/RichTextArea/RichTextArea.md
- Discussion points: https://github.com/andy-goryachev-oracle/Test/blob/main/doc/RichTextArea/RichTextAreaDiscussion.md
- API specification (javadoc): https://cr.openjdk.org/~angorya/RichTextArea/javadoc
- RichTextArea RFE: https://bugs.openjdk.org/browse/JDK-8301121
- Behavior doc: https://github.com/andy-goryachev-oracle/jfx/blob/8301121.RichTextArea/doc-files/behavior/RichTextAreaBehavior.md
- CSS Reference: https://cr.openjdk.org/~angorya/RichTextArea/javadoc/javafx.graphics/javafx/scene/doc-files/cssref.html
- InputMap (v3): https://github.com/andy-goryachev-oracle/Test/blob/main/doc/InputMap/InputMapV3.md
- Previous Draft PR: https://github.com/openjdk/jfx/pull/1374

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Commit messages:
 - whitespace
 - 8301121: RichTextArea Control (Incubator)

Changes: https://git.openjdk.org/jfx/pull/1524/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1524&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301121
  Stats: 38592 lines in 208 files changed: 38569 ins; 9 del; 14 mod
  Patch: https://git.openjdk.org/jfx/pull/1524.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1524/head:pull/1524

PR: https://git.openjdk.org/jfx/pull/1524