update ci workflows

[akellbl4]

unifies the way workflows defined, updates actions, gives names to jobs

Common:

• run jobs on push only for master (we don't need to run them for every push to every branch, when PR is opened jobs will be run for each push, now it runs twice)
• update actions/checkout to v3
• add names to jobs for better readability in PRs

Backend:

• move ci-test-backend.yml → .github/workflows/ci-backend.yml because if we have more backend jobs they will leave there, otherwise if name on the top of the file is the same they will be grouped
• use name: backend for grouping all of the backend related jobs

Frontend:

• move size-limit job to ci-frontend.yml

Site:

• rename build-site to build because it's already prefixed with root name

[github-actions]

size-limit report 📦

Path	Size
public/embed.mjs	2.02 KB (0%)
public/remark.mjs	72.37 KB (-0.01% 🔽)
public/remark.css	8.2 KB (0%)
public/last-comments.mjs	35.51 KB (0%)
public/last-comments.css	3.79 KB (0%)
public/deleteme.mjs	12.05 KB (0%)
public/counter.mjs	749 B (0%)

[codecov]

Codecov Report

Merging #1418 (3e19591) into master (6625fac) will not change coverage.
The diff coverage is n/a.

❗ Current head 3e19591 differs from pull request most recent head 65ed21a. Consider uploading reports for the commit 65ed21a to get more accurate results

@@           Coverage Diff           @@
##           master    #1418   +/-   ##
=======================================
  Coverage   58.12%   58.12%           
=======================================
  Files         131      131           
  Lines        2909     2909           
  Branches      743      743           
=======================================
  Hits         1691     1691           
  Misses       1087     1087           
  Partials      131      131           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 6625fac...65ed21a. Read the comment docs.

[akellbl4]

@umputun
this snipper should do the thing. Run actions on every push and avoid running them twice on PR

pull_request:
  types: [opened, reopened]

https://github.com/umputun/remark42/pull/1418/files#diff-d534d457d2f453ff292b326309bebf3d6b2f7e067ca4247038b61df22d09c728R13

[akellbl4]

Close and reopen in order to kickoff actions with recent changes