converted from github wiki to respec

[himorin]

converted and added text from https://github.com/Japan-Daisy-Consortium/documents/wiki/Text-to-Speech-of-Electronic-Documents-Containing-Ruby:-User-Requirements

Note:

• Please only check respec format (e.g. section order is correct), but not text contents themselves. Please review them after this merged.
• id is not assigned to section, since header text might be updated during our review (to be addressed before FP-NOTE)
• added some references (as informative; default for Note), but some should missing. Please review them after this merged.
• some of note sections are actually quotations from other specs, but I am not sure what style we should apply here
• one text contents correction applied, for quoted text from JLREQ Figure 241. (these in the original wiki version were actually totally wrong description...)

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[himorin]

updated with affiliation of @murata2makoto . I've also checked again, that no respec error is reported, nor sectioning mismatch with original version in wiki.

so, let me merge this here.