RFR: 8344367: Fix mistakes in FX API docs

[Nir Lisker]

A batch of typo and grammar fixes that were found by the spellchecker.

Integration can wait until RDP 1/2.

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Commit messages:
 - More corrections
 - Batch typo fixes
 - Fix mistakes in OpenJFX docs

Changes: https://git.openjdk.org/jfx/pull/1642/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1642&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344367
  Stats: 76 lines in 40 files changed: 0 ins; 0 del; 76 mod
  Patch: https://git.openjdk.org/jfx/pull/1642.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1642/head:pull/1642

PR: https://git.openjdk.org/jfx/pull/1642