Fix #4 Update @actions/core

See here for further details:
https://github.blog/changelog/2020-10-01-github-actions-deprecating-set-env-and-add-path-commands

node_modules/@actions/core/README.md

@@ -82,7 +82,14 @@ try {
     core.warning('myInput was not set');
   }
   
+  if (core.isDebug()) {
+    // curl -v https://github.com
+  } else {
+    // curl https://github.com
+  }
+
   // Do stuff
+  core.info('Output to the actions build log')
 }
 catch (err) {
   core.error(`Error ${err}, action may still succeed though`);
@@ -137,4 +144,4 @@ const core = require('@actions/core');
 var pid = core.getState("pidToKill");
 
 process.kill(pid);
-```
+```