feat: added ability to use the "extends" settings

This is done to be able to use shared configurations

docs: Added docs for the extends feature

fix: syntax error, due to rebase

src/preInstall.task.js

@@ -0,0 +1,21 @@
+const path = require('path');
+const core = require('@actions/core');
+const exec = require('./_exec');
+
+/**
+ * Pre-install extra dependecies
+ * @returns {Promise<void>}
+ */
+module.exports = async extras => {
+  if (!extras) {
+    return Promise.resolve();
+  }
+
+  const _extras = extras.replace(/['"]/g, '').replace(/[\n\r]/g, ' ');
+
+  const { stdout, stderr } = await exec(`npm install ${_extras}`, {
+    cwd: path.resolve(__dirname, '..')
+  });
+  core.debug(stdout);
+  core.error(stderr);
+};