Feature Release

Changelog:

New Features:

• Annotations now fully accessible via keyboard controls and will be announced by a screen reader on opening.
• Help screen fully accessible via keyboard and screen reader.
• Copyright is now settable via the Collection panel in Story and will persist through saves. (@sdumetz)
• Integrated support for ktx2 (basisu) and meshopt decoders. (@sdumetz)

Bug fixes:

• Fixed bug that was overwriting overlay maps when working with multi-model scenes.
• Fixed property regressions that caused #293 & #294.
• Addressed #290 by updating the scene bounds whenever a model's visibility changes.
• Fixed #287 by handling mouse release on a splitter with no previous mouse down.

Misc:

• Unused file cleanup (@sdumetz)
• ff-* libraries moved to source tree (@sdumetz)
• node-sass module replaced with sass to improve compatibility and address vulnerabilities (@sdumetz)