style.css: Reformat and improve checkbox accessibility

Previously the expandable checkboxes were { display: none; } which made
them impossible to focus via the keyboard. Here we change it to {
opacity: 0; position: absolute; }, so it becomes keyboard-focusable.
Then we add an outline to the <label> when the checkbox is focused so
users could visually identify that the checkbox has been focused.

1 files changed, 0 insertions, 3 deletions

diff --git a/TODO b/TODO
index e318057..e8cc5fa 100644
--- a/TODO
+++ b/TODO
@@ -10,6 +10,3 @@
 
 * Unit tests
 * Refactoring other stuff
-
-Accessibility:
-* Those labels in css state machines are not keyboard focusable!