fix(docs): fix and update some examples

[zyriab]

Some examples were outdated and did not run anymore so I fixed them.
I also added some more examples to make things clearer.

As for the note removed from the add command's docs, it has been made a non-issue with release 0.8.4 by adding a space after the -- in order to make a comment.

Just a note, on the add example, this line does not actually add the color picker's value to the element but the string my.value.

I doubled check and I can log my.value and got a hex.
I didn't know how to fix it but the example is still important to keep so I just left it :)

Talking about this:

on change add { --accent-color: my.value } to document.body