fix: correct typo that prevented mixin load

Author: Nicolò Maria Mezzopera

src/components/LControlLayers.vue

@@ -4,7 +4,7 @@ import Control from '../mixins/Control.js';
 
 export default {
   name: 'LControlLayers',
-  mnixins: [Control],
+  mixins: [Control],
   props: {
     collapsed: {
       type: Boolean,

src/components/LControlScale.vue

@@ -4,7 +4,7 @@ import Control from '../mixins/Control.js';
 
 export default {
   name: 'LControlScale',
-  mnixins: [Control],
+  mixins: [Control],
   props: {
     maxWidth: {
       type: Number,

src/components/LControlZoom.vue

@@ -4,7 +4,7 @@ import Control from '../mixins/Control.js';
 
 export default {
   name: 'LControlZoom',
-  mnixins: [Control],
+  mixins: [Control],
   props: {
     zoomInText: {
       type: String,