Properly prefix the icon path for the select arrow icon.

See https://gitlab.tugraz.at/VPU/WebComponents/datatableview/issues/2

packages/common/styles.js

-import {css} from 'lit-element';
+import {css, unsafeCSS} from 'lit-element';
+import {getIconSVGURL} from './vpu-icon.js';
 
 /**
  * We want to have "neutral" colors here
@@ -121,7 +122,7 @@ export function getGeneralCSS() {
         select:not(.select) {
             -moz-appearance: none;
             -webkit-appearance: none;
-            background: calc(100% - 0.2rem) center no-repeat url("/local/vpu-common/icons/chevron-down.svg");
+            background: calc(100% - 0.2rem) center no-repeat url("${unsafeCSS(getIconSVGURL('chevron-down'))}");
             background-size: 25%;
             border-color: black;
             border-width: 1px;

packages/common/vpu-icon.js

@@ -17,7 +17,7 @@ const errorIcon = `
 </svg>
 `;
 
-function getIconSVGURL(name) {
+export function getIconSVGURL(name) {
     return commonUtils.getAssetURL('local/vpu-common/icons/' + encodeURI(name) + '.svg');
 }