implemented button to make document positions optional

Signed-off-by: Stephan Richter <s.richter@srsoftware.de>

frontend/src/routes/document/Position.svelte

@@ -1,6 +1,7 @@
 <script>
     import { onMount }       from 'svelte';
     import { useTinyRouter } from 'svelte-tiny-router';
+    import { t }             from '../../translations.svelte';
 
     import LineEditor        from '../../Components/LineEditor.svelte';
     import MarkdownEditor    from '../../Components/MarkdownEditor.svelte';
@@ -23,13 +24,17 @@
     function movedown(){
         movePos(pos.number,1);
     }
+
+    async function toggleOptional(ev){
+        const ok = await submit(`${prefix}.optional`,!pos.optional);
+        if (ok) pos.optional = !pos.optional;
+    }
 </script>
 
 <style>
     .move{
         vertical-align: middle;
     }
-
     tr > *:nth-child(1){
         text-align: right;
     }
@@ -66,6 +71,7 @@
             <span onclick={moveup}>⏫</span>
             {/if}
             <span onclick={() => drop(pos.number)}>❌</span>
+            <span class="symbol" onclick={toggleOptional} title={t(pos.optional?'optional position':'fixed position')}>{pos.optional?'':''}</span>
             <span onclick={movedown}>⏬</span>
             {/if}
         </td>