Availability column name change (#1474)

* change the availability column group name

* Add explanation to missing one table

* fix node test

---------

Co-authored-by: DanielRyanSmith <danielrsmith@google.com>

Author: DanielRyanSmith

frontend/src/static/js/components/test/webstatus-stats-missing-one-impl-chart-panel.test.ts

@@ -211,6 +211,14 @@ describe('WebstatusStatsMissingOneImplChartPanel', () => {
       <div slot="header" id="missing-one-implementation-list-header">
         Missing features on 2024-01-01 for Chrome:
         <a href="/?q=id%3Agrid+OR+id%3Ahtml+OR+id%3Ajs+OR+id%3Abluetooth">4 features</a>
+        <div class="table-description">
+           * This table represents feature values
+           <strong>
+             as of today
+           </strong>
+           ,
+          and not at the selected timestamp.
+         </div>
       </div>
     `;
     expect(header).dom.to.equal(expectedHeader);

frontend/src/static/js/components/webstatus-stats-missing-one-impl-chart-panel.ts

@@ -79,6 +79,11 @@ export class WebstatusStatsMissingOneImplChartPanel extends WebstatusLineChartPa
           overflow-x: auto;
           white-space: nowrap;
         }
+        .table-description {
+          font-size: 14px;
+          font-style: italic;
+          margin: 8px 0;
+        }
       `,
     ];
   }
@@ -252,6 +257,10 @@ export class WebstatusStatsMissingOneImplChartPanel extends WebstatusLineChartPa
         <a href="${this.featureListHref}"
           >${this.missingFeaturesList.length} features</a
         >
+        <div class="table-description">
+          * This table represents feature values <strong>as of today</strong>,
+          and not at the selected timestamp.
+        </div>
       </div>
       ${this.renderMissingFeaturesTable()}
     `;