Add Products.CMFPlone is preferred location to identify Plone core pa… (#1776)

* Add Products.CMFPlone is preferred location to identify Plone core packages
- See plone/Products.CMFPlone#3594 (comment)

ping @petschki

* Fix typos

Author: stevepiercy

docs/contributing/core/index.md

@@ -167,7 +167,8 @@ git pull
 ## Edit packages
 
 First identify the names of the Plone packages you want to work on.
-If you do not know, you can ask in the [Plone Community Forum](https://community.plone.org/).
+If you do not know, you can open an issue in the Plone GitHub repository for [`Products.CMFPlone`](https://github.com/plone/Products.CMFPlone/issues/), and someone might identify the source within a few days.
+You can also ask in the [Plone Community Forum](https://community.plone.org/).
 Only a few packages are in {file}`src/` by default.
 
 Next create a new file {file}`buildout.local.cfg`, and add the names of packages that you want to develop under the `auto-checkout` list.
@@ -262,7 +263,7 @@ bin/test --all
 ```
 
 Plone uses [Playwright](https://playwright.dev/) to run robot tests.
-`plone.app.robotframework` provides a script to install Playwrite browsers.
+`plone.app.robotframework` provides a script to install Playwright browsers.
 
 ```shell
 ./bin/rfbrowser init