Broken links to 1.2 spec

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Like reported in yaml/yaml-spec#172:
Links like https://yaml.org/spec/1.2/#ns-tag-char will be redirected and lose the url fragment.
I think the old page has to be reinstated.
There could be a link on top pointing to the new format and a watermark. Maybe even Javascript that does lead to the correct page including the fragment. Which should be 1.2.1 and not 1.2.2 btw

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So @ingydotnet pushed some fixes.
The current version doesn't work for spec/1.2/index.html urls though.
Also without Javascript one just sees a blank page.

In my opinion this should be improved.