Bug 1503671 - Add to about:telemetry a link to the Probe Dictionary r=chutten

This may help users discover more about the probes being collected.

toolkit/content/aboutTelemetry.js

@@ -1783,6 +1783,7 @@ function setupPageHeader() {
     "https://docs.telemetry.mozilla.org/",
     "https://firefox-source-docs.mozilla.org/toolkit/components/telemetry/telemetry/index.html",
     "https://telemetry.mozilla.org/",
+    "https://telemetry.mozilla.org/probe-dictionary/",
   ];
   let htmlLink = document.querySelectorAll("#home-section > ul > li > a");
   htmlLink.forEach((a, index) => {

toolkit/content/aboutTelemetry.xhtml

@@ -142,6 +142,7 @@
           <li>&aboutTelemetry.firefoxDataDoc;</li>
           <li>&aboutTelemetry.telemetryClientDoc;</li>
           <li>&aboutTelemetry.telemetryDashboard;</li>
+          <li>&aboutTelemetry.telemetryProbeDictionary;</li>
         </ul>
       </section>
 

toolkit/locales/en-US/chrome/global/aboutTelemetry.dtd

@@ -23,6 +23,7 @@
 <!ENTITY aboutTelemetry.firefoxDataDoc "The <a>Firefox Data Documentation</a> contains guides about how to work with our data tools.">
 <!ENTITY aboutTelemetry.telemetryClientDoc "The <a>Firefox Telemetry client documentation</a> includes definitions for concepts, API documentation and data references.">
 <!ENTITY aboutTelemetry.telemetryDashboard "The <a>Telemetry dashboards</a> allow you to visualize the data Mozilla receives via Telemetry.">
+<!ENTITY aboutTelemetry.telemetryProbeDictionary "The <a>Probe Dictionary</a> provides details and descriptions for the probes collected by Telemetry.">
 
 <!ENTITY aboutTelemetry.showInFirefoxJsonViewer "Open in the JSON viewer">