This seeks to remove the "_" from the key presses of snapshots and inline
runs in the documentation. The "_" no longer does anything, but got legacy
reasons at the moment we can't actually allow "_" to be an input to a
"faked" keypress in the docs and snapshots.
Removing these clears the way to letting "_" have the same status as any
other character.
See #1994.
* 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>
