Localize time units on activity heatmap (#21570)

Previously, the months and days were hardcoded into English

* Closes #15541

## Screenshots
### English

![image](https://user-images.githubusercontent.com/20454870/197410352-1b28a637-ce19-41ae-b4e5-27955555b082.png)

### German

![image](https://user-images.githubusercontent.com/20454870/197410455-f243ca84-807f-476e-b8ed-c24e827bfc2d.png)

### Spanish

![image](https://user-images.githubusercontent.com/20454870/197410366-55202ca5-08f9-4152-8f9d-d5eeebd532ef.png)

### Italian

![image](https://user-images.githubusercontent.com/20454870/197410385-75f754dd-e845-4444-8a04-472a8f45b617.png)

### Portuguese
This one has a bit of overflow

![image](https://user-images.githubusercontent.com/20454870/197410414-b91f962e-77e9-4cc7-990b-01c0fc0cbd0b.png)

Signed-off-by: Yarden Shoham <hrsi88@gmail.com>
Co-authored-by: Gusted <williamzijl7@hotmail.com>
Co-authored-by: silverwind <me@silverwind.io>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

web_src/js/components/ActivityHeatmap.vue

@@ -25,6 +25,10 @@ export default {
       type: Array,
       default: () => [],
     },
+    locale: {
+      type: Object,
+      default: () => {},
+    }
   },
   data: () => ({
     colorRange: [
@@ -36,10 +40,6 @@ export default {
       'var(--color-primary-dark-4)',
     ],
     endDate: new Date(),
-    locale: {
-      contributions: 'contributions',
-      no_contributions: 'No contributions',
-    },
   }),
   computed: {
     sum() {