Added workflows + dependabot

[AB-xdev]

Fixes #3

TL;DR
Added dependabot and the following workflows:

• checkBuild
  • Builds LTS variants of the jar for Java 8,11 and 17 (currently commented out)
  • Builds a jar for the XDEV IDE
• test-deployment
  • Allows creation of manual deployments (for SNAPSHOTS)
• release
  • Checks if the build works (for Java 8)
  • Prepares the release by removing -SNAPSHOT and creating a new version on GitHub
  • Publishes all variants (Java 8 + 11) to maven central/ossrh
  • Builds dependency-information for Java 11 (Java 8 has no dependencies)
  • Builds the jar for the xdev-ide (won't be uploaded to the release and ~30-90 days available - can be rebuilt if required)
  • Prepares for the next development iteration: Increments version + adds SNAPSHOT (it's a bit complicated when there is a variable inside)

ℹ️ The release workflow should be tested at least once, after it got merged