Works beside HUD and text-effect plugins

• New: MC GUI now works beside plugins and packs that change Minecraft's text shader, such as BetterHud, HUDEngine, ItemsAdder's text effects and Oraxen's animated glyphs. At startup MC GUI reads the other plugin's pack, or the server's own pack set in server.properties, and merges its text shader into MC GUI's, so both should work. The console says what was merged. A plugin that writes its pack after MC GUI starts is merged on the next restart. Turn it off with resource-pack.merge-shaders: false.
• Fixed: with another plugin's text shader beside MC GUI's (HUDEngine's merged by Nexo, for one), 26.3 could refuse the whole server pack ("Failed to reload resources"). MC GUI's shaders now load beside anyone's.
• When another plugin's pack lands on top of MC GUI's, MC GUI's is sent again before the next page opens, as it already was for Dialog Engine.
• New: clip-path (polygon(), circle(), ellipse(), inset()) works on pages, and the page's CSS now styles what is inside an inline SVG, :hover included. Hexagon and other shaped buttons made on mcgui.dev now draw in game as they do in the preview.
• Tip: on an overlay page, colour under 50% opacity with only the world behind it isn't drawn in game. Use 0.5 or more for anything that must show.