feat: set up FFI

Signed-off-by: Sphericalkat <me@kat.bio>

.gitignore

@@ -0,0 +1,10 @@
+# https://dart.dev/guides/libraries/private-files
+# Created by `dart pub`
+.dart_tool/
+
+# Avoid committing pubspec.lock for library packages; see
+# https://dart.dev/guides/libraries/private-files#pubspeclock.
+pubspec.lock
+
+# FVM Version Cache
+.fvm/