Add additional acceptable css properties

[factcondenser]

picking up where #258 left off

[flavorjones]

OK, the remaining failure looks like it's because of these additional CSS properties being allowed (the test is probably descriptive and not prescriptive). I'll take a closer look.

[flavorjones]

Closing. I really want additions to the allowlist to be driven by real user needs.

For example, I'm not comfortable with position in this list, because untrusted content could then be superimposed on other parts of a web page.

Another example, accent-color which I know as primarily used for styling web forms, which aren't appropriate for Loofah sanitization.

Sorry it took so long to circle back on this and close the loop. I'm open to additions to the allowlist, but I do want to be able to to have a conversation with the users who are asking.