Implementation of picture addition button in editor.

frontend/src/app/pages/publication-edition/publication-edition.component.html

@@ -38,7 +38,7 @@
                             <button type="button" matTooltip="Click to insert a title 1 section" (click)="insertTitle(3)">
                                 H3
                             </button>
-                            <button type="button" disabled matTooltip="Click to insert a picture">
+                            <button type="button" matTooltip="Click to insert a picture" (click)="selectAPicture()">
                                 <mat-icon>image</mat-icon>
                             </button>
                             <button type="button" matTooltip="Click to insert a link" (click)="insertLink()">