v0.11.8

AlgebraOfGraphics v0.11.8

Diff since v0.11.7

Merged pull requests:

• Prepare v0.10.9 (#685) (@jkrumbiegel)
• Include v0.10.9 backport in changelog (#686) (@jkrumbiegel)
• Improve all-missings group handling (#689) (@jkrumbiegel)