Build: Add intuitive names to Travis jobs

Otherwise it's hard to see at a glance that a particular job is running
on Firefox ESR, for example.

Closes jquerygh-4596

.travis.yml

@@ -9,44 +9,44 @@ env:
   - NPM_SCRIPT=test:browserless
 matrix:
   include:
-    # Run browser tests only on one Node.js version to save time.
-    - node_js: "12"
+    - name: "Browser tests: full build, Chrome & Firefox stable"
+      node_js: "12"
       env:
         - NPM_SCRIPT="test:browser"
         - BROWSERS="ChromeHeadless,FirefoxHeadless"
       addons:
         chrome: stable
         firefox: latest
-    # Run tests against the slim build.
-    - node_js: "12"
+    - name: "Browser tests: slim build, Chrome stable"
+      node_js: "12"
       env:
         - NPM_SCRIPT="test:slim"
         - BROWSERS="ChromeHeadless"
       addons:
         chrome: stable
-    # Run tests against the no-deprecated build.
-    - node_js: "12"
+    - name: "Browser tests: no-deprecated build, Chrome stable"
+      node_js: "12"
       env:
         - NPM_SCRIPT="test:no-deprecated"
         - BROWSERS="ChromeHeadless"
       addons:
         chrome: stable
-    # Run ES module tests.
-    - node_js: "12"
+    - name: "Browser tests: ES modules build, Chrome stable"
+      node_js: "12"
       env:
         - NPM_SCRIPT="test:esmodules"
         - BROWSERS="ChromeHeadless"
       addons:
         chrome: stable
-    # Run AMD tests.
-    - node_js: "12"
+    - name: "Browser tests: AMD build, Chrome stable"
+      node_js: "12"
       env:
         - NPM_SCRIPT="test:amd"
         - BROWSERS="ChromeHeadless"
       addons:
         chrome: stable
-    # Run tests on Firefox ESR as well.
-    - node_js: "12"
+    - name: "Browser tests: full build, Firefox ESR"
+      node_js: "12"
       env:
         - NPM_SCRIPT="test:browser"
         - BROWSERS="FirefoxHeadless"