Massive restructure of plugin API

plug-api/plugos-syscall/asset.ts

@@ -0,0 +1,15 @@
+import { base64Decode } from "../../plugos/asset_bundle/base64.ts";
+import { syscall } from "./syscall.ts";
+
+export async function readAsset(
+  name: string,
+  encoding: "utf8" | "dataurl" = "utf8",
+): Promise<string> {
+  const data = await syscall("asset.readAsset", name);
+  switch (encoding) {
+    case "utf8":
+      return new TextDecoder().decode(base64Decode(data));
+    case "dataurl":
+      return "data:application/octet-stream," + data;
+  }
+}