feat: add metrics endpoint

[wa0x6e]

🧿 Current issues / What's wrong ?

From https://github.com/snapshot-labs/pitches/issues/18

💊 Fixes / Solution

This PR add a /metrics endpoint, exposing some basic express/node metrics, as well as custom metrics

🚧 Changes

• Expose metrics via /metrics endpoint

🛠️ Tests

• Go to http://localhost:3005/metrics

[codecov]

Codecov Report

Merging #134 (483eb9e) into main (2e43c1a) will decrease coverage by 2.14%.
Report is 1 commits behind head on main.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main     #134      +/-   ##
==========================================
- Coverage   60.80%   58.66%   -2.14%     
==========================================
  Files          18       19       +1     
  Lines        1319     1367      +48     
  Branches       91       92       +1     
==========================================
  Hits          802      802              
- Misses        510      557      +47     
- Partials        7        8       +1     

Files Changed	Coverage Δ
src/api.ts	0.00% <0.00%> (ø)
src/helpers/metrics.ts	0.00% <0.00%> (ø)
src/helpers/sentry.ts	11.62% <0.00%> (ø)
src/index.ts	0.00% <0.00%> (ø)
src/lib/queue.ts	0.00% <0.00%> (ø)
src/lib/storage/aws.ts	26.25% <0.00%> (ø)
src/lib/storage/file.ts	84.31% <0.00%> (ø)
src/webhook.ts	0.00% <0.00%> (ø)

[Todmy]

utACK