Fix heatmap first color being unused (#22157)

vue3-calendar-heatmap has the behaviour that the first and second colors
are mapped to values null and 0, meaning the second color was not used
as intended for values > 0. I think this is a behaviour change from
previous vue2 version that was missed during the upgrade.

This change makes first and second values the same, so the heatmap can
now use one additional color for meaningful values.

Before:
<img width="710" alt="Screenshot 2022-12-18 at 09 17 58"
src="https://user-images.githubusercontent.com/115237/208288347-df4973af-8ebd-4582-b828-bec948ffdf60.png">

After:
<img width="709" alt="Screenshot 2022-12-18 at 09 18 15"
src="https://user-images.githubusercontent.com/115237/208288350-e0b85aa2-6925-4a37-83d2-89e2518c91ce.png">

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

web_src/js/components/ActivityHeatmap.vue

@@ -32,6 +32,7 @@ export default {
   },
   data: () => ({
     colorRange: [
+      'var(--color-secondary-alpha-70)',
       'var(--color-secondary-alpha-70)',
       'var(--color-primary-light-4)',
       'var(--color-primary-light-2)',
@@ -50,6 +51,12 @@ export default {
       return s;
     }
   },
+  mounted() {
+    // work around issue with first legend color being rendered twice and legend cut off
+    const legend = document.querySelector('.vch__external-legend-wrapper');
+    legend.setAttribute('viewBox', '12 0 80 10');
+    legend.style.marginRight = '-12px';
+  },
   methods: {
     handleDayClick(e) {
       // Reset filter if same date is clicked