RFR: 8347362: RichTextArea Demo Apps Build Integration

[Andy Goryachev]

Added ant build to the RichTextAreaDemo project.

## Building

Build: run `ant` command in the project directory.

## Running Demos

Use the following commands to run demos build in the previous section:

Code Area Demo: `ant run-codearea-demo`

Notebook Demo: `ant run-notebook-demo`

Rich Editor Demo: `ant run-richeditor-demo`

RichTextArea Tester: `ant run-richtextarea-demo`

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Commit messages:
 - build and run demos with ant

Changes: https://git.openjdk.org/jfx/pull/1672/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1672&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8347362
  Stats: 132 lines in 2 files changed: 130 ins; 1 del; 1 mod
  Patch: https://git.openjdk.org/jfx/pull/1672.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1672/head:pull/1672

PR: https://git.openjdk.org/jfx/pull/1672