Add spoiler tags

Boards can have spoiler processors enabled on them now.

Signed-off-by: Alek Ratzloff <alekratz@gmail.com>

board/migrations/0004_board_spoilers.py

@@ -0,0 +1,18 @@
+# Generated by Django 4.1b1 on 2022-07-20 07:57
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ("board", "0003_board_hidden"),
+    ]
+
+    operations = [
+        migrations.AddField(
+            model_name="board",
+            name="spoilers",
+            field=models.BooleanField(default=False),
+        ),
+    ]