Updates to Player Guide Brief, Player Guide Full, and start of GM Guide Brief

[LockerM]

I did a full read through of the Player Guide Brief and the Player Guide Full and made large-scale modifications and updates to the language and specific rules across both documents. Hoping that the merge of these rules will prepare us for the next stage.

In most cases, I streamlined the language or made clarifications to the rules to help make them more explicit based on experience at the table or through reading them more carefully.

I made updates to both documents to remove references to old rules and include references to new ones.

I also added the Status Condition Dead and added rules behind that to create an initial thesis of the rules and language behind what happens if players are defeated or if they fail the Epic Event after being Knocked Out.

I am open to feedback and modification of my language choices on any of these areas.

In this PR I also included the basis for the GM Guide Brief which I will continue to work on and hope to update prior to merge. Otherwise I can delete the file and we can merge just the changes to Player Guide Brief and Full.

[LockerM]

Removed GM Guide Brief from the PR in latest commit.

Updated mkdocs files with new branding materials (logo + colors).

[LockerM]

Resolved comments outstanding in the PR. Removed Death from PGF to be revisited later as a potential addition in the GM Guide for optional rules to handle Death.

Added new branding elements in the stylesheet to update the github pages site as well.

Only comment I didn't update or address yet was the Glossary/Hypernym comment for Character vs. Creature. Let me know if there's anything else outstanding besides for that before we merge.