Documentation: Expand instructions for Certificate Authority setup

[notevenaperson]

Motivation and Context

I found the documentation for using pywb Certificate Authority difficult to use for adding the CA to Chromium, as I had never done something like that before. I attempted to make the 4th step as clear as possible, "4. You may need to agree to "Trust this CA" to identify websites." (Agree where?) Also, the ordering of the paragraphs was somewhat disjointed.

[notevenaperson]

These are some links that could be useful in the instructions, but I omitted them to keep the documentation brief, and also free from hand-waving solutions to untested resources.

• https://support.mozilla.org/en-US/kb/setting-certificate-authorities-firefox
• https://stackoverflow.com/questions/7580508/getting-chrome-to-accept-self-signed-localhost-certificate/15076602