shim more buffer methods, and fs methods

getting importer plugin to work,

src/shims/globals.js

@@ -24,6 +24,18 @@ function installBuffer() {
 
       return new Uint8Array(data);
     },
+    alloc: function (size, fill, encoding) {
+      const buf = new Uint8Array(size);
+
+      if (fill !== undefined) {
+        buf.fill(typeof fill === "string" ? fill.charCodeAt(0) : fill);
+      }
+
+      return buf;
+    },
+    allocUnsafe: function (size) {
+      return new Uint8Array(size);
+    },
     concat: function (arrays) {
       const total = arrays.reduce((sum, a) => sum + a.length, 0);
       const result = new Uint8Array(total);
@@ -39,6 +51,20 @@ function installBuffer() {
     isBuffer: function (obj) {
       return obj instanceof Uint8Array;
     },
+    byteLength: function (str, encoding) {
+      return new TextEncoder().encode(str).length;
+    },
+    isEncoding: function (encoding) {
+      return [
+        "utf8",
+        "utf-8",
+        "ascii",
+        "binary",
+        "base64",
+        "hex",
+        "latin1",
+      ].includes((encoding || "").toLowerCase());
+    },
   };
 }