Add title for pages others than packages

[TixieSalander]

Currently only packages pages (for example) have a dedicated <title>.

It could be great for other pages to have it to.
Un non exhaustive list of the one that could receive one:

• https://flora.pm/about
• https://flora.pm/categories
• https://flora.pm/categories/algorithms
• https://flora.pm/packages
• https://flora.pm/packages/@hackage
• https://flora.pm/packages/@hackage/ADPfusion/0.5.2.0 (same title as https://flora.pm/packages/@hackage/ADPfusion/)
• https://flora.pm/packages/@hackage/ADPfusion/0.5.2.0/dependencies (same title as https://flora.pm/packages/@hackage/ADPfusion/)
• https://flora.pm/search?q=foo
  https://flora.pm/search?q=foo&page=2
• https://flora.pm/sessions/new

I may take more time in the future to index a more exhaustive list who could help me start suggesting of a pattern for every kinds of page titles. But that ticket is a start for now