feat: add FEN block support and related assets

Introduced a new FEN block feature, including a PHP snippet to render FEN diagrams, a new CSS file for chessboard styling, font integration, and blueprint updates. Adjusted asset paths and file references for consistency.

assets/css/chess.css

@@ -0,0 +1,5 @@
+@font-face {
+    font-family: 'Case';
+    src: url('../fonts/CASEFONT.TTF');
+    font-weight: normal;
+}

assets/fonts/pgn4web-font-LiberationSans.css

@@ -24,3 +24,8 @@
     font-weight: bold;
 }
 
+@font-face {
+    font-family: 'Case';
+    src: url('CASEFONT.TTF');
+    font-weight: normal;
+}

assets/js/png4web.js

@@ -1474,7 +1474,7 @@ var InitialHalfMoveClock = 0;
 var PieceImg = new Array(new Array(6), new Array(6));
 var ClearImg;
 
-var ImagePath = 'images';
+var ImagePath = '/images';
 var ImagePathOld = null;
 var imageType = 'png';
 var defaultImagesSize = 40;