Add comment with an explanation

Author: nking07049925

src/webgl/ShaderGenerator.js

@@ -19,6 +19,8 @@ function shadergenerator(p5, fn) {
     if (shaderModifier instanceof Function) {
       let generatorFunction;
       if (options.parser) {
+        // #7955 Wrap function declaration code in brackets so anonymous functions are not top level statements, which causes an error in acorn when parsing
+        // https://github.com/acornjs/acorn/issues/1385
         const sourceString = `(${shaderModifier.toString()})`;
         const ast = parse(sourceString, {
           ecmaVersion: 2021,