Add `<title>` to more pages

[tophf]

Suggesting to add <title> to ensure there's meaningful text in the tab title and in browser history.

• in reports
• in conversations only <h2> is added currently: https://github.com/greasyfork-org/greasyfork/blob/37a73ed7634a293d210a8798a8f02107b495cfb9/app/views/conversations/show.html.erb#L1-L3