feat: display stats about total & active TUs on proposals

This patch brings in two new features:
- when viewing proposal listings, there is a new Statistics section,
  containing the total and active number of Trusted Users found in the
- when viewing a proposal directly, the number of active trusted users
  assigned when the proposal was added is now displayed in the details

Closes #323

Signed-off-by: Kevin Morris <kevr@0cost.org>
2 jobs for proposal-stats in 3 minutes and 44 seconds (queued for 1 second)