increased character limit keyword icon

thanks cazier for pointing out this issue and providing a PR https://github.com/vabene1111/recipes/pull/46

cookbook/migrations/0031_auto_20200407_1841.py

@@ -0,0 +1,18 @@
+# Generated by Django 3.0.4 on 2020-04-07 16:41
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('cookbook', '0030_recipeingredient_note'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='keyword',
+            name='icon',
+            field=models.CharField(blank=True, max_length=16, null=True),
+        ),
+    ]