DOC: Add descriptions to the Pixi tasks

[VeckoTheGecko]

Fixes None

Before:

❯ pixi task list           
Tasks that can run on this machine:
-----------------------------------
docs, docs-linkcheck, docs-watch, lint, numpydoc-lint, tests, tests-notebooks, typing
Task  Description

After:

❯ pixi task list
Tasks that can run on this machine:
-----------------------------------
docs, docs-linkcheck, docs-watch, lint, numpydoc-lint, tests, tests-notebooks, typing
Task             Description
docs             Build the documentation.
docs-linkcheck   Verify all links in documentation don't 404.
docs-watch       Build and auto-rebuild the documentation on changes.
lint             Run all pre-commit linting hooks.
numpydoc-lint    Lint public API docstrings with numpydoc.
tests            Run the test suite.
tests-notebooks  Run the user guide example notebooks as tests.
typing           Run static type checking with mypy.

Feel free to make any edits @erikvansebille - I feel like this makes things a lot more accessible for new devs :)

[erikvansebille]

Looks very good! Only comment would be that I find the table header =(Task. Description) a bit confusingly formatted now, between the full list of tasks and the rows of the table. Can that header row be removed? I think it's self-explanatory?

And do we also need the first line with all the tasks?

A shorter version would then be

❯ pixi task list
Tasks that can run on this machine:
-----------------------------------
docs             Build the documentation.
docs-linkcheck   Verify all links in documentation don't 404.
docs-watch       Build and auto-rebuild the documentation on changes.
lint             Run all pre-commit linting hooks.
numpydoc-lint    Lint public API docstrings with numpydoc.
tests            Run the test suite.
tests-notebooks  Run the user guide example notebooks as tests.
typing           Run static type checking with mypy.

[VeckoTheGecko]

Only comment would be that I find the table header =(Task. Description) a bit confusingly formatted now, between the full list of tasks and the rows of the table. Can that header row be removed?

Yes, you're right - this is confusing. Hopefully the formatting improves with future versions of pixi - but this is out of our control on our end