build: publish beta package when building pull request

[scolladon]

Explain your changes

---

Improve our PR with the publishing of a beta package Improve our contributing guide so anyone can install the beta package easily and do the QA

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (a86a6ff) to head (9f4f81d).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #838 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 37 37 Lines 1044 1044 Branches 113 113 ========================================= Hits 1044 1044 ```

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[codeclimate[bot]]

Code Climate has analyzed commit 9f4f81d3 and detected 0 issues on this pull request.

View more on Code Climate.

[github-actions[bot]]

Published under beta-838 npm channel.

$ sfdx plugins:install sfdx-git-delta@beta-838

[github-actions[bot]]

Shipped in release v5.39.0. You can install the new version using the version number or the latest-rc channel

$ sfdx plugins:install sfdx-git-delta@latest-rc
$ sfdx plugins:install sfdx-git-delta@v5.39.0

Happy incremental deployment!