Add period_period_period ligature

[amitkparekh]

Addesses #106, #84.

Weights:

• SSm Book
• SSm Book Italic

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Only committed the new glyph files.

[kiliman]

As I mentioned in the previous PR, you need to commit all changes from extract.js since they are dependent on the subroutines generated. It's kind of hard to make independent PRs for different glyphs if the are all in the same OTF file. Once the glyphs are approved in the source repo, you should simply add them all at once here as a single PR.