Add button-input

src/app/components/CalendarEventForm.svelte

@@ -180,7 +180,7 @@
           </div>
           <Button
             data-tip="Add an image"
-            class="button button-neutral tip"
+            class="button button-neutral button-input tip"
             onclick={selectFiles}
             disabled={loading}>
             {#if $uploading}

src/lib/components/button.css

@@ -102,6 +102,11 @@
   .button-xs {
     @apply h-7 gap-1 rounded-xl px-2 text-xs;
   }
+  /* for a button beside an .input/.input-editor in a flex row: stretch to the
+     row height instead of fixing one, since input height varies by theme */
+  .button-input {
+    @apply h-auto self-stretch;
+  }
 
   /* shapes */
   .button-block {