Added a check for the previous character to the  *em* Tokenizer. Needed to pass any tests where the em block starts with a punctuation character (e.g. commonmark example 368)

Modifies the em rule after the block tokens are generated to detect known reflinks and skip over them so they don't get mistakenly italicized.

Now fixes three more cases

Reflinks are replaced with the string 'aaaa' of equal length to hide any asterisks or underscores that might have been inside, since these should not be included. Then, the resulting string is matched to the em regex. The positions of the captures are then used on the original string.

Fixes examples 391, 397, 399, 400, 401, 431, 443, 475, 476, 479, and 480

Found a few more cases of redundant symbols in addition to fixes suggested during review.

mask reflinks in a separate function

And remove redundant unused capture group.

Beginning and End delimiters for EM and Strong must be searched in a separate regex to work without lookbehinds. This invalidates the regex that skips over blocks (code, html, etc.) that take precedence over EM or Strong blocks.

Getting around this means we must now mask not only reflinks, but all enclosed blocks which were previously just skipped over in the Regex.

Add one check for overlapping Strong block when testing EM, now passes Commonmark 390 and 471

Co-authored-by: Tony Brix <tony@brix.ninja>

Co-authored-by: Tony Brix <tony@brix.ninja>

… into EmphasisFixes