docs: vpn: Add documentation for evaluation of vpn protocols

[maurerle]

T-X created a pretty cool table to evaluate VPN uplink protocols used in gluon on this hedgedoc:
https://md.chaotikum.org/zRkW6JXXQs-8WCnwdtig5w?view

To give it more visibility, I would like to add it to the docs as suggested somewhere.

I hope this is fine for you @T-X and @rotanid ?

[rotanid]

my first thought was, that your text and commit message talk about "mesh protocol" while the content isn't about mesh protocols but about VPNs ;-)

[T-X]

@maurerle oh, had totally forgotten about this table already. I like the idea of adding it to the docs, thanks for the conversion effort!

I think "fastd, null@l2tp, offloaded" should have "Single interface for all peers" -> "no" though? I'm also wondering if it could be nice to add a link to the Mesh VPN MTU page onto the "MTU overhead" heading?

Also would be nice if someone could do a quick check for the l2tp kernel module if it supports multi-threading, on some live device or x86 VM.

[T-X]

I'm also wondering what to do with the Tunneldigger entry. As all of its mentions was removed from the docs otherwise. Maybe add a link to the according community package on Github onto "Tunneldigger" and add "inofficial" in brackets? (or even "deprecated"?)

Edit: As no new maintainer of it has stepped up so far, maybe "deprecated" might be more appropriate for now?

[T-X]

And another thought, would it maybe make sense to place it higher instead of at the bottom as it's a nice, quick, first overview?

(Edit: and then rename it to "Protocols Overview"?)

[T-X]

"former supported" -> "formerly supported" (adverb)

and add "ones" after "formerly supported"?

Also no comma in this first sentence. (rule in English: if the sentence/clause can't exist on its own then no comma; I know, unintuitive for us native German speakers, where we use a lot more commas :D)

[grische]

Some suggestions

[maurerle]

Thanks @rotanid , @T-X and @grische - I updated the PR according to your review and suggestion.
I hope we can merge this soon :)

[grische]

@maurerle I can't see any changes. Did you forget to push the commits?

[maurerle]

Sorry, I pushed to the wrong repository (ffac).. Thanks

[grische]

There's a comma missing, otherwise LGTM.