Documentation improvement

[Kerbalnut]

Most of the comments in the script (mainly in the top parameters block) haven't been edited since the original 2018 version, and may be unfriendly to non-technical users who just wish to use this script once to clean up a PDF quickly and fix the "active content" email bounce-back error they've been getting.

This includes install instructions in this very README, which could be explained a bit better in a "don't make me think" sort of way. I try to avoid writing such "assume the user knows nothing, explain how to do everything from step #0" instructional guides anymore, but perhaps this will appeal to a larger audience, and I tend to only use this tool once every 2 years myself (when I'm sending out resumes) so I forget what the hell I was doing here regularly as well.

At the very least, include screenshots of what parts to edit, define alternate install methods clearly, and refine the language a bit. Possibly in the future, break the script down in to easy-to-inspect blocks, write a simple build script that amends them together, so that what is quickly becoming a monolithic batch script is easy to inspect & build yourself before you run it? We'll see. Tracking in Issue #6

• Define install methods clearly (K.I.S.S.)
• Define use method examples
• Add screenshots
• Add animated gifs for main readme page
• Refine rest of README language, which might me outdated. (Re-structure)
• Explain batch is Windows-only