add external-script plugin

src/plugins/external-script.js

@@ -0,0 +1,24 @@
+const scriptReg = /<script[^>]*src=["|'](.*)["|']>[^\w]*<\/script>/
+const asyncReg = /<script[^>]*\s+async/
+const deferReg = /<script[^>]*\s+defer/
+
+function handleExternalScript (html) {
+  const scriptMatch = html.match(scriptReg)
+
+  if (scriptMatch && scriptMatch.length > 1) {
+    const script = document.createElement('script')
+    script.src = scriptMatch[1]
+
+    if (asyncReg.test(scriptMatch[0])) script.setAttribute('async', '')
+    if (deferReg.test(scriptMatch[0])) script.setAttribute('defer', '')
+
+    const target = document.querySelector('#main')
+    target.appendChild(script)
+  }
+}
+
+const install = function (hook) {
+  hook.afterEach(handleExternalScript)
+}
+
+window.$docsify.plugins = [].concat(install, window.$docsify.plugins)