Adding unpack as cli command and exposing via index.ts for typescript usage. (#5)

src/index.ts

@@ -1,6 +1,7 @@
 // Default export includes everything (backward compatibility)
 export * from "./cli/init.js";
 export * from "./cli/pack.js";
+export * from "./cli/unpack.js";
 export * from "./node/files.js";
 export * from "./node/sign.js";
 export * from "./node/validate.js";