This is the part where the [guide](https://textual.textualize.io/guide/widgets/#default-css) explains the `DEFAULT_CSS` feature, leaving a small amount of css in `hello04.css`. However, the App class still links to the css file from the previous version (`hello03.css`). This PR fixes that and updates to the recent one.
While in this part of the docs we do want to keep the bell (see key02), it
was an error in the code that it included this event in key01. Removing it
from here because adding this bit of code for key02 is a key (no pun) part
of the docs.
The surrounding text in the documentation states that Screen is imported
from textual.screen, but the code was importing the class from textual.app.
Further, I was getting warnings from pyright that I was using a class that
wasn't exported from the module I was importing from.
* Initial layout guide stuff
* More docs on layout - grid
* Continuing grid docs
* Grid gutter and spans guide
* Improvements to layout docs for horizontal, vertical, dock, and begin describing layers
* Update center layout example to reflect new yield order
* More updates to layout guide, mostly offset stuff
* More layout guide, "Putting it all together"
* Updates to layout guide page
* Small rewording of dock layout in guide
* Apostrophe
* Typo
* Small design tweak to combining layouts example
* Typos, tidying up
* Small reword
* Some updates to docs/guide/layout/grid
* calc fix
Co-authored-by: Will McGugan <willmcgugan@gmail.com>
