Rename repository to match the WordPress.org slug

[moorscode]

As we want to match the repository name with the WordPress.org slug of the plugin, these need to be synced.

The name should be: acf-content-analysis-for-yoast-seo

Update the following files:

• [ ] composer.json
• [ ] README.md
• [ ] readme.txt
• [ ] package.json
• [ ] .github/*.md

After release:

• [ ] Rename the repository to match

Update the slack channel reference to the repo.

[moorscode]

After which we can move on with https://github.com/Yoast/yoast-acf-analysis/issues/87