Add start-date prop to force placing of date picker in date

src/components/date-picker/picker.vue

@@ -39,6 +39,7 @@
                         :steps="steps"
                         :format="format"
                         :value="internalValue"
+                        :start-date="startDate"
 
                         v-bind="ownPickerProps"
 
@@ -204,6 +205,9 @@
                 type: Boolean,
                 default: false
             },
+            startDate: {
+                type: Date
+            },
             size: {
                 validator (value) {
                     return oneOf(value, ['small', 'large', 'default']);