docs: More flexible share links

[ddxv]

Example client: thirdgate.dev

v.0.1

oa.thirdgate.dev/collect?clicks

oa.thirdgate.dev/s/myshare1
oa.thirdgate.dev/s/myshare2


dash.thirdgate.dev -> DASH
dash.thirdgate.dev/apps -> DASH
...

In the current MVP version all share links will need to point to the /s/ endpoint eg oa.thirdgate.dev/s/$myurlcode.

It's possible to imagine that for share codes specifically there might be a few better ways, all of which need some documenation for how to do with nginx.

oa.thirdgate.dev/collect?clicks

# shortest possible subdomain, no `/s` required
s.thirdgate.dev/myshare1
s.thirdgate.dev/myshare2

# no subdomain, all traffic points to /s/
thirdgate.dev/s/myshare1
thirdgate.dev/s/myshare2


dash.thirdgate.dev -> DASH
dash.thirdgate.dev/apps -> DASH