chore: specify breaking changes

Added `canvas-constructor/browser` export.
Added `canvas-constructor/cairo` export.
Added `canvas-constructor/skia` export.
Added `registerFont` in `/cairo` and `/skia`.
Added non-standard package-specific support in dedicated classes.
Removed automatic module detection in utilities.
Refactored internals to work without dependencies for browser environments.
Refactored types so they are always accurate and never yield type errors.

BREAKING CHANGE: Removed main export at `canvas-constructor`.
BREAKING CHANGE: Dropped Node 8, 10, and 12 support

Author: favna