refactor: simplify base.js (#3473)

lnbits/static/js/lnurl.js

@@ -0,0 +1,23 @@
+window.decryptLnurlPayAES = (success_action, preimage) => {
+  let keyb = new Uint8Array(
+    preimage.match(/[\da-f]{2}/gi).map(h => parseInt(h, 16))
+  )
+
+  return crypto.subtle
+    .importKey('raw', keyb, {name: 'AES-CBC', length: 256}, false, ['decrypt'])
+    .then(key => {
+      let ivb = Uint8Array.from(window.atob(success_action.iv), c =>
+        c.charCodeAt(0)
+      )
+      let ciphertextb = Uint8Array.from(
+        window.atob(success_action.ciphertext),
+        c => c.charCodeAt(0)
+      )
+
+      return crypto.subtle.decrypt({name: 'AES-CBC', iv: ivb}, key, ciphertextb)
+    })
+    .then(valueb => {
+      let decoder = new TextDecoder('utf-8')
+      return decoder.decode(valueb)
+    })
+}