Add RGB color system

[alppp]

adds full RGB color support using the §x§R§R§G§G§B§B wire format (1.16+ spigot standard).
degrades gracefully on unmodded clients.

features:

• 16.7M RGB colors via §x or &#RRGGBB shorthand
• gradients (§g/&g) with two color endpoints
• rainbow (§y/&y) - static per-character hue cycle
• wave (§w/&w) - animated sine offset, freezes in HUD cache
• dinnerbone (§j/&j) - flipped characters
• all legacy §0-f and §k-o still work
• line wrapping preserves colors and effects across breaks
• config toggles: enableRGBColors, enableTextEffects, enableAmpersandConversion
• sign rendering support

Examples :

--- Basic RGB (&#RRGGBB syntax) ---
&#FF0000Red &#00FF00Green &#0000FFBlue

--- Legacy colors ---
&cRed &aGreen &bBlue &eYellow

--- Rainbow ---
&qRainbow text here&r normal

--- Wave ---
&zWavy text here&r normal

--- Dinnerbone ---
&vFlipped text&r normal

--- Gradient ---
&g&#FF0000&#0000FFSmooth red to blue gradient&r done

--- Wave survives color change ---
&z&#FF0000Red wave &aGreen wave still going&r stopped

--- Dinnerbone survives color change ---
&v&cFlipped red &aFlipped green &bFlipped blue&r normal

--- Reset clears everything ---
&z&q&vAll effects on&r All effects off

--- Gradient + bold ---
&g&#FF0000&#FFFF00&lBold gradient text&r done

--- Invalid edge cases (should render literally) ---
&#GGGGGGinvalid hex &#FFnot enough digits &# nothing

--- Normal formatting ---
Just a normal &c with &l bold &r reset

--- Long gradient wrap test ---
&g&#FF0000&#00FF00This is a really long gradient message that should wrap across multiple chat lines to verify the color interpolation continues smoothly after the line break point

related PRs (all required):

• Add & color code awareness to font methods GTNHLib#328 - & code awareness in width/size/trim methods
• Add color code support for text rendering Hodgepodge#829 - chat wrap, text field scroll, anvil limit, sign input
• Add color system integration BetterQuesting#199 - editor buttons, color picker, gradient wrap, monochrome fix