Pro 8355 add task info

[BoDonkey]

Summary

Summarize the changes briefly, including which issue/ticket this resolves. If it closes an existing Github issue, include "Closes #[issue number]"
This PR adds a new tutorial and additional examples to the @apostrophecms/task module reference. This was based on a request from Val because he was struggling to find examples of how to write a task. Closes PRO-8355.

What are the specific steps to test this change?

For example:

1. Run the website and log in as an admin
2. Open a piece manager modal and select several pieces
3. Click the "Archive" button on the top left of the manager and confirm that it should proceed
4. Check that all pieces have been archived properly

What kind of change does this PR introduce?

(Check at least one)

• Bug fix
• New feature
• Refactor
• Documentation
• Build-related changes
• Other

Make sure the PR fulfills these requirements:

• It includes a) the existing issue ID being resolved, b) a convincing reason for adding this feature, or c) a clear description of the bug it resolves
• The changelog is updated
• Related documentation has been updated
• Related tests have been updated

If adding a new feature without an already open issue, it's best to open a feature request issue first and wait for approval before working on it.

Other information:

[linear]

PRO-8355 Add code example of command line tasks

[boutell]

• Address tasks that overlap with existing modules or tasks - make sure people don't get lost in their attempt to find those due to this article - point to our import/export module which already provides CSV export, point to our existing (but basic) universal generate task for content generation.
• But then go ahead with your examples - maybe you prefer a task for CSV, maybe you prefer a custom generation task, etc.
• Do not generate bad CSV without proper escaping, it will come back to us as a sad bug report someday. Use a real csv npm module.