Support umlauts in links

[philmtd]

It would be nice if there was an option for supporting german umlauts in the links, e.g. this is what markdown-toc creates:

+ [Frachtaufträge](#frachtauftrage)

This is what I desire:

+ [Frachtaufträge](#frachtaufträge)

GitLab creates anchors with umlauts so currently I need to manually edit all anchors with umlauts.

[jonschlinkert]

Agree, we should support this. Want to do a pr?

[philmtd]

Yep I just did a PR: #81 👍

[mootari]

I'd like to muddy the scope of this issue a bit by suggesting that transliteration would be another option:

+ [Frachtaufträge](#frachtauftraege)

German umlauts ("ä", "ö", "ü") can also be written as "ae", "oe", "ue". For more examples from various languages check out the transliteration package.