Make mark downloaded color overrideable

(CSS var in getThemeCSS() required)

assets/dbp-signature.html.ejs

@@ -49,6 +49,7 @@
             --dbp-override-warning-bg-color: #ffe183;
             --dbp-override-warning-text-color: black;
             --dbp-override-success-bg-color: #259207;
+            --dbp-override-downloaded-bg-color: #9fdf9f;
         }
     </style>
 

src/dbp-official-signature-pdf-upload.js

@@ -600,6 +600,10 @@ class OfficialSignaturePdfUpload extends ScopedElementsMixin(DBPSignatureLitElem
                 white-space: nowrap;
             }
 
+            .downloaded {
+                background: var(--dbp-downloaded-bg-color);
+            }
+
             #pdf-preview .button.is-cancel {
                 color: #e4154b;
             }

src/dbp-qualified-signature-pdf-upload.js

@@ -706,6 +706,10 @@ class QualifiedSignaturePdfUpload extends ScopedElementsMixin(DBPSignatureLitEle
                 white-space: nowrap;
             }
 
+            .downloaded {
+                background: var(--dbp-downloaded-bg-color);
+            }
+
             #pdf-preview .button.is-cancel {
                 color: #e4154b;
             }

src/dbp-signature-lit-element.js

@@ -411,6 +411,6 @@ export default class DBPSignatureLitElement extends BaseLitElement {
         this.signedFilesToDownload = files.length;
         this._("#file-sink").files = files;
         const div = this.shadowRoot.querySelector('#' + id);
-        div.style.background='#c8dcc8';
+        div.classList.add('downloaded');
     }
 }