Add all matroska tags

[invliD]

I found some more tags I need in addition to #135, so I figured I'd just add them all.

[codecov]

Codecov Report

Merging #136 (12285ff) into master (76a505c) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #136   +/-   ##
=======================================
  Coverage   99.32%   99.32%           
=======================================
  Files          22       22           
  Lines        1180     1180           
=======================================
  Hits         1172     1172           
  Misses          4        4           
  Partials        4        4           

Impacted Files	Coverage Δ
elementtable.go	100.00% <ø> (ø)
elementtype.go	100.00% <ø> (ø)

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[at-wat]

Overall looks good to me. It would be better to add comments for deprecated elements.

[invliD]

Yeah, I intentionally added the deprecated ones (specifically all those that were included in at least one version of the standard), because I actually have older files that include some of these elements, and they wouldn't be parseable without them defined here. I'll add the comments to those elements.

[at-wat]

LGTM