Fix typos in rend-spec-ng.txt and tor-spec.txt
There are a number of typos and inconsistencies in in `torspec/proposals/224-rend-spec-ng.txt`. I've created a branch to fix them:
**Branch:** typos-rend-spec-ng
**Repository:** https://github.com/teor2345/torspec.git
**Changes:**
* Fix misspellings, inconsistent field names, and missing INT_8() specifiers. (Inferred from context.)
* Consistently use _LEN rather than _LENGTH for field lengths in 224-rend-spec-ng.txt. (8 replacements made.)
There is also a typo in `torspec/tor-spec.txt` that is fixed in:
**Branch:** typos-tor-spec
**Repository:** https://github.com/teor2345/torspec.git
**Changes:**
* Fix typo where "yes" is clearly intended to be "yet"
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