Update boundaryFalloff setting and add panel subsection heading styles

- Changed boundaryFalloff from 1 to 0 in main.js settings for improved behavior.
- Added new languages ES, PT, JP

js/main.js

@@ -62,7 +62,7 @@ const settings = {
   seamBandWidth:    0.5,
   textureSmoothing: 0,
   capAngle:         20,
-  boundaryFalloff:  1,
+  boundaryFalloff:  0,
   symmetricDisplacement: false,
   useDisplacement: false,
 };