On page TOC title missing from language strings

[Protonotarios]

Hi! I've just added Greek translation #19 [EDIT: I've cancelled this and made a new pull request - see below]. The funny thing is that the reason I'd started translating in the first place was to translate just one string actually: the on page TOC title in frontend. But it's not there 😄

Can you please add it?

[Protonotarios]

P.S. I just saw that another important frontend string is missing: "Permanent link:" in tooltip.

[Protonotarios]

I just added the title strings missing #21 on toc.html.twig. I hope it's ok given that I have just learned the very existence of twig! I am still working on the tooltip but it's a bit difficult for me since the language dependent replacements occur at the end of Toc.php while the tooltip is generated very early in the code.