Docs: Moved misc/fonts/README.txt to docs/FONTS.txt. + tweaks

imgui.h

@@ -2144,7 +2144,7 @@ struct ImFontAtlas
     // After calling Build(), you can query the rectangle position and render your pixels.
     // You can also request your rectangles to be mapped as font glyph (given a font + Unicode point),
     // so you can render e.g. custom colorful icons and use them as regular glyphs.
-    // Read misc/fonts/README.txt for more details about using colorful icons.
+    // Read docs/FONTS.txt for more details about using colorful icons.
     IMGUI_API int               AddCustomRectRegular(unsigned int id, int width, int height);                                                                   // Id needs to be >= 0x110000. Id >= 0x80000000 are reserved for ImGui and ImDrawList
     IMGUI_API int               AddCustomRectFontGlyph(ImFont* font, ImWchar id, int width, int height, float advance_x, const ImVec2& offset = ImVec2(0,0));   // Id needs to be < 0x110000 to register a rectangle to map into a specific font.
     const ImFontAtlasCustomRect*GetCustomRectByIndex(int index) const { if (index < 0) return NULL; return &CustomRects[index]; }