LanguageToolPython 2.4.0

The main change in v2.4.0 is to support LanguageTool's 5.0 update, which supports more languages and errors.

Also made some miscellaneous changes:

• remove dependencies we don't need anymore and other stale things (Dockerfile)
• fix 'JDK 14 could not be parsed' issue
• fix enable/disable spellchecking features
• correct Match types with utils.correct() functionality (and add to README)