Clarify the repo licensing sources in public docs

[CoreyRDean]

Non-technical summary

• Clarifies where BlitzForge's real licensing terms live in the repository instead of implying a repo-wide MIT-style grant.
• Gives contributors and redistributors one place to find the checked-in notice files that actually govern the compiler core and bundled third-party libraries.
• Reduces the chance of someone making reuse or packaging decisions from an overstated README summary.

Technical summary

• replace the README's broad "open-source / MIT-style" claim with wording that points readers at the checked-in license notices
• expand the README license section to link the inherited Blitz3D core notice at src/blitzrc/LICENSE.TXT
• add LICENSES.md as a pointer map to the authoritative license files for src/blitzrc, libogg, libvorbis, and the bundled FreeImage tree
• validation: verified every linked notice path exists and ran git diff --check
• breaking changes: none

Additional notes

• Trade-off: this documents the current tree honestly without inventing a new top-level license file or relicensing the repo.
• Intentionally deferred: any repo-wide licensing decision or new canonical root LICENSE artifact should be made explicitly by maintainers, not inferred in an automation pass.
• Remaining gap: GitHub still shows no repository license metadata until the project chooses and adds a root-level license file or equivalent canonical licensing surface.