Disabled CSS test using `all: revert !important`

[ffoodd]

Where could this stand:

• webextension only?
• a new info / manual checks level?

Related to #344 #345 #320

FWIW, inspiration from Miriam Suzanne on Twitter — and it all started with a joke :D

Here's the code to try:

#no-css {
    all: revert !important
}