Typos

A few typo corrections:

--- The specification says:

" Modifiers and Enrichers procesing an XLIFF Document that contains <skeleton> elements MUST NOT change those elements."

It should say:

"Modifiers and Enrichers **processing** an XLIFF Document that contains **a <skeleton> element** MUST NOT change **that elements**.


-- The specification says:

"Extractors creating an XLIFF Document with <skeleton> elements MUST leave the <skeleton> element empty if and only if they specify
the attribute href."

It should say:

" Extractors creating an XLIFF Document with **a <skeleton> element** MUST leave the <skeleton> element empty if and only if **the
element specifies** the attribute href."

-ys