add fontstash and nanovg port from heimdall

vendor/nanovg/gl/vert.glsl

@@ -0,0 +1,19 @@
+#ifdef NANOVG_GL3
+	uniform vec2 viewSize;
+	in vec2 vertex;
+	in vec2 tcoord;
+	out vec2 ftcoord;
+	out vec2 fpos;
+#else
+	uniform vec2 viewSize;
+	attribute vec2 vertex;
+	attribute vec2 tcoord;
+	varying vec2 ftcoord;
+	varying vec2 fpos;
+#endif
+
+void main(void) {
+	ftcoord = tcoord;
+	fpos = vertex;
+	gl_Position = vec4(2.0*vertex.x/viewSize.x - 1.0, 1.0 - 2.0*vertex.y/viewSize.y, 0, 1);
+}