RFR: 8355774: RichTextArea: provide mechanism for CSS styling of highlights

[Andy Goryachev]

Adding missing APIs related to styling the highlights with CSS:

![Screenshot 2025-05-07 at 15 08 53](https://github.com/user-attachments/assets/e37062b4-9804-40a7-872d-830fe0f584c1)



Adds methods to the `RichParagraph.Builder`:


        /**
         * Adds a wavy underline (typically used as a spell checker indicator) with the specified style name(s).
         * <p>
         * The corresponding styles should define CSS properties applicable to {@link javafx.scene.shape.Path}.
         *
         * @param start the start offset
         * @param length the end offset
         * @param css the style name(s)
         * @return this {@code Builder} instance
         * @since 25
         */
        public Builder addWavyUnderline(int start, int length, String ... css) {



        /**
         * Adds a highlight with the specified style name(s).
         * Use translucent colors to enable multiple highlights in the same region of text.
         * <p>
         * The corresponding styles should define CSS properties applicable to {@link javafx.scene.shape.Path}.
         *
         * @param start the start offset
         * @param length the end offset
         * @param css the style name(s)
         * @return this {@code Builder} instance
         * @since 25
         */
        public Builder addHighlight(int start, int length, String ... css) {



Also adding similar methods to the `SimpleViewOnlyStyledModel` class:


    /**
     * Adds a highlight of the given color to the specified range within the last paragraph,
     * with the specified style name(s).
     *
     * @param start the start offset
     * @param length the length of the highlight
     * @param css the highlight style name(s)
     * @return this model instance
     * @since 25
     */
    public SimpleViewOnlyStyledModel highlight(int start, int length, String ... css) {


    /**
     * Adds a wavy underline (typically used as a spell checker indicator)
     * to the specified range within the last paragraph, with the specified style name(s).
     *
     * @param start the start offset
     * @param length the length of the highlight
     * @param css the highlight style name(s)
     * @return this model instance
     * @since 25
     */
    public SimpleViewOnlyStyledModel addWavyUnderline(int start, int length, String ... css) {

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Commit messages:
 - tab
 - css

Changes: https://git.openjdk.org/jfx/pull/1802/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1802&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8355774
  Stats: 128 lines in 4 files changed: 110 ins; 8 del; 10 mod
  Patch: https://git.openjdk.org/jfx/pull/1802.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1802/head:pull/1802

PR: https://git.openjdk.org/jfx/pull/1802