Project Mode feature

[worksofliam]

Changes

• Peek all references on export functions
• Go to local export implementation or program from prototype
• Auto-import for local export functions not previously defined
  • Depends on Auto import for system APIs #33
• If the active editor is a include file (.rpgleinc), somehow show which other sources include this source.
  • Add command for programmatically showing a list of references in the references view microsoft/vscode#112507

Checklist

• have tested my change
• updated relevant documentation
• Remove any/all console.logs I added
• eslint is not complaining
• have added myself to the contributors' list in the README
• for feature PRs: PR only includes one feature enhancement.