Special Characters in header generate invalid navigation link

[norbertbede]

english behaviour: My first Header = my-first-header

not working use case My first Header č = my-first-header-č => the proper would be my-first-header-c

Impact: we can't use our languages like: SLOVAK, HUNGARIAN..etc

xref https://medium.com/@mhagemann/the-ultimate-way-to-slugify-a-url-string-in-javascript-b8e4a0d849e1