docs: add a basic FAQ section

docs/astro.config.mjs

@@ -27,6 +27,10 @@ export default defineConfig({
               label: 'Quick Start',
               link: '/intro/quick-start/',
             },
+            {
+              label: 'FAQ',
+              link: '/intro/faq/',
+            },
           ],
         },
         {

docs/src/content/docs/intro/faq.mdx

@@ -0,0 +1,19 @@
+---
+title: "FAQ"
+description: "Frequently asked questions about Emigrate."
+---
+
+## Why no `down` migrations?
+
+> Always forward never backwards.
+
+Many other migration tools support `down` migrations, but in all the years we have been
+doing migrations we have never needed to rollback a migration in production,
+in that case we would just write a new migration to fix the problem.
+
+In our experience the only time `down` migrations are useful is in development,
+and in such case you just revert the migration manually and fix the `up` migration.
+
+The benefit of this is that you don't have to worry about writing `down` migrations, and you can focus on writing the `up` migrations.
+This way you will only ever have to write `down` migrations when they are really necessary instead of for every migration
+(which makes it the exception rather than the rule, which is closer to the truth).