Add download props to Legend component, export downloadSvg util

Author: keller-mark

src/components/legends/Legend.vue

@@ -8,13 +8,17 @@
             :getScale="getScale"
             :getStack="getStack"
             :clickHandler="clickHandler"
+            :showDownloadButton="showDownloadButton"
+            :downloadName="downloadName"
          />
         <ContinuousLegend v-if="legendType === 'continuous'" 
             :variable="variable"
             :lWidth="lWidth"
             :lItemHeight="lItemHeight"
             :getScale="getScale"
             :getStack="getStack"
+            :showDownloadButton="showDownloadButton"
+            :downloadName="downloadName"
         />
     </div>
 </template>
@@ -69,6 +73,14 @@ export default {
         },
         'clickHandler': {
             type: Function
+        },
+        'showDownloadButton': {
+            type: Boolean,
+            default: false
+        },
+        'downloadName': {
+            type: String,
+            default: 'legend'
         }
     },
     data() {

src/index.js

@@ -50,6 +50,7 @@ import Expected from './expected';
 
 // Other
 import { EVENT_TYPES, EVENT_SUBTYPES, EVENT_SUBTYPE_RESETS } from './history/base-events';
+import { downloadSvg } from './helpers';
 
 // Reference: https://stackoverflow.com/questions/28282295/getbbox-of-svg-when-hidden
 const _getBBox = SVGGraphicsElement.prototype.getBBox;   
@@ -120,4 +121,5 @@ export {
     // Other
     computedParam,
     EVENT_TYPES, EVENT_SUBTYPES, EVENT_SUBTYPE_RESETS,
+    downloadSvg,
 }