WebUSB: Add troubleshooting links to docs and error modal. (#251)

Author: microbit-mark

help.html

@@ -413,6 +413,9 @@ <h2 id="WebUSB">WebUSB</h2>
 
     <p>If you see the message 'no compatible devices found' when you try to connect, 
     you may need to <a href="https://microbit.org/guide/firmware">update the micro:bit firmware.</a></p>
+
+    <p>For any issues using these features, please read our guide on <a href="https://support.microbit.org/a/solutions/articles/19000105428-webusb-troubleshooting/">
+        WebUSB troubleshooting</a>.</p>
 
     <h3>Flash</h3>
     <p>To flash the micro:bit from the browser, use the <strong>Connect</strong> button to pair the device

lang/en.js

@@ -96,6 +96,7 @@ var language = {
       'unavailable': 'With WebUSB you can program your micro:bit and connect to the serial console directly from the online editor.<br/>Unfortunately, WebUSB is not supported in this browser. We recommend Chrome, or a Chrome-based browser to use WebUSB.',
       'find-more': 'Find Out More'
     },
+    'troubleshoot': 'Troubleshoot',
     'close': 'Close',
     'request-repl': 'Send CTRL-C for REPL',
     'request-serial': 'Send CTRL-D to reset',