Freeze tutorials: fixes and cleanup

- Move JS code samples to JS folder (future-proofing for other
  languages)
- Make "Freeze a Trust Line" tutorial interactive
- Add necessary functionality to interactive_tutorial helper JS
- Rework freeze a trust line tutorial/code sample to make an incoming
  line from another address and make looking up trust lines a
  full-fledged step

content/_code-samples/freeze/js/check-global-freeze.js

@@ -0,0 +1,34 @@
+// Dependencies for Node.js.
+// In browsers, use <script> tags as in the example demo.html.
+if (typeof module !== "undefined") {
+  // gotta use var here because const/let are block-scoped to the if statement.
+  var xrpl = require('xrpl')
+  var { AccountRootFlags } = require('xrpl/dist/npm/models/ledger')
+}
+  
+// Connect -------------------------------------------------------------------
+async function main() {
+  console.log("Connecting to Mainnet...")
+  const client = new xrpl.Client('wss://s1.ripple.com')
+  await client.connect()
+
+  const my_address = 'rf1BiGeXwwQoi8Z2ueFYTEXSwuJYfV2Jpn';
+
+  // Request account info for my_address to check account settings ------------
+  const response = await client.request(
+    {command: 'account_info', account: my_address })
+  const settings = response.result
+  const lsfGlobalFreeze = xrpl.LedgerEntry.AccountRootFlags.lsfGlobalFreeze
+
+  console.log('Got settings for address', my_address);
+  console.log('Global Freeze enabled?',
+              ((settings.account_data.Flags & lsfGlobalFreeze) 
+              === lsfGlobalFreeze))
+
+  await client.disconnect()
+
+  // End main()
+} 
+
+main().catch(console.error)
+