Fontique: Support registering a font with custom family name and `FontInfo`

[nicoburns]

The use case for this is supporting CSS web fonts (@font-face)

Requirements:

• Register a font, overriding the family name
• It should be possible to register multiple fonts with the same family name
• It should be possible to specify custom FontInfo for each font (overriding the data from the font file).

Non-requirements:

• Supporting font collections (.ttc files). Web fonts do not support font collections, so for the purposes of this API we can assume that

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Ideally it should also be possible to register custom fonts in a separate "layer" to the system fonts such that:

• A different set of custom fonts can be used for (e.g. each page/tab), while still sharing system fonts (not entirely duplicating the database)
• It is possible to easily "roll back"/"unregister" the custom fonts (e.g. when navigating between pages / documents)

(but perhaps this is a separate feature)