implement CFF2 parsing

[Connum]

Description

fix #249

• add parsers that can be shared by other variable font related tables
• add operators for CFF2 table parsing
• parse glyph data in its default form, ignoring variations
• add some preparations for later variable font support

This PR does not handle font variation itself - it allows to load the data including glyph outlines and all other data from the CFF2 table. The glyphs will have their default form without any variations, so advanceWith will com from the glyph outline. But together with #576 it is an important step on the way to adding support for modern variable fonts.

Motivation and Context

CFF2 offers even better compression and is oprimized for variable fonts. Many variable fonts use CFF2 and couldn't be loaded before.

How Has This Been Tested?

Added tests for the different parsers as well as parsing of the exampler CFF2 table from the Microsoft specs.

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I did npm run test and all tests passed green (including code styling checks).
• I have added tests to cover my changes.
• My change requires a change to the documentation.
• I have updated the README accordingly.
• I have read the CONTRIBUTING document.

[ILOVEPIE]

Looks good to me.