Support character-specific story variations

[oubiwann]

Namely, in specific areas ("rooms").

[oubiwann]

This could include:

1. Header metadata indicating
   • that the content is character-sensitive
   • what character attribute(s) the content is sensitive to (gender, race, class, stat-level)
   • whether the Default section should be used for all characters, and each other section simply appending its content to the Default, or
   • to completely replace each characteristic-specific variation with the content in each section
2. The use of sections in the Markdown for the characteristic-specific changes to content, e.g., Bards, Wisdom > 15, Halflings, Favoured Terrain, etc.