README.md: Missed a semicolon in the dump files nginx example.

Signed-off-by: Martin Stone <martin@d7415.co.uk>
(cherry picked from commit 0714123043e1fd5dad172d35af684ba0ec21116d)
walkthrough.md: Added the dump sharing lines to example nginx configuration, commented out.

Signed-off-by: Martin Stone <martin@d7415.co.uk>
(cherry picked from commit 71fe32d7e9bb47c68bcf5b5a57fc668a88950854)
Arthur: Add (optional) link to dumps next to fluxbb link in Arthur.

Signed-off-by: Martin Stone <martin@d7415.co.uk>
(cherry picked from commit 133e1569c2de384b93859dd80c3efae14ad344ed)
(cherry picked from commit d7d1494a02285cf81f44c12c8bb6928e9935c0ef)
Arthur: Fixed dump link.

Signed-off-by: Martin Stone <martin@d7415.co.uk>