Auto generate changelog and readme entries

[wjrosa]

Changes proposed in this Pull Request:

This PR changes how we update changelog.txt and readme.txt entries by making it more automated. You can add new entries by running npm run changelog and filling in the required information. Upon merging to the' develop' branch, the entry will automatically merge with readme.txt and changelog.txt.

On a next iteration, we will try to create the entries automatically based on the PR description or title. We will also include the PR ID as part of the changelog entry.

Testing instructions

Code review should be enough. You can also draft another PR with a branch created from this one (dev/auto-generate-changelog-and-readme-entries) and test the new command and see the new PR description template.

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• Covered with tests (or have a good reason not to test in description ☝️)
• Added changelog entry in both changelog.txt and readme.txt (or does not apply)
• Tested on mobile (or does not apply)

Post merge

• Added testing instructions to the Release Testing Instructions wiki page (or does not apply)
• Added the needs docs label (or does not apply)
• Included this PR in the Release Thread scope (or does not apply)

cc @diegocurbelo