refactor global css

[alee]

• limit the scope of global DOM element styling in main.scss to font size, font family etc., not colors
• add game.scss with styles specific to the game UI
• remove header global styles

Current issues

• header modal width set to 100% is stretching past the side of the screen for the player detail modal and bot warning modal

dark text over dark background issues

• Role header text in the player modal
• accomplishment card text
• events text
• resources / inventory
• phase information
• other players