fix: base64 encode OPA policy.wasm (#24)

The GitHub Action on remote repos does not have access to the
action repo's assets.  This change base64 encodes the policy.wasm
so that it gets compiled into the action's `dist/index.js` entrypoint.

action.yaml

@@ -39,3 +39,7 @@ inputs:
 runs:
   using: 'node12'
   main: 'dist/index.js'
+
+branding:
+  icon: 'layers'  
+  color: 'purple'  

src/opa.js

@@ -1,7 +1,7 @@
 "use strict";
 
-const fs = require("fs");
 const { loadPolicy } = require("@open-policy-agent/opa-wasm");
+const { policyWasmBase64 } = require("./opa-policy.js");
 
 /**
  * Uses ./policy/resource-changes.rego OPA policy to examine the JSON generated
@@ -10,9 +10,9 @@ const { loadPolicy } = require("@open-policy-agent/opa-wasm");
  * @returns {Object} Resource and output changes in the tfplan
  */
 const getPlanChanges = async (planJson) => {
-  const policyWasm = fs.readFileSync("./policy/policy.wasm");
-
+  const policyWasm = Buffer.from(policyWasmBase64, "base64");
   const policy = await loadPolicy(policyWasm);
+
   const results = policy.evaluate(planJson);
 
   let changes;