Add a script to build on ios

I usually do these steps manually each time.

scripts/build_ios.sh

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+
+if [ -z ${FASTLANE_PASSWORD+x} ]; then
+    echo "Must set FASTLANE_PASSWORD"
+    exit 1
+fi
+
+set -eu
+
+cd "$(dirname "$0")"
+cd ../
+
+# Check for uncommitted changes
+if [[ $(git status -s | grep -v '??') ]]; then
+    echo "Uncommitted Changes."
+    echo "Exiting"
+    exit 1
+fi
+
+flutter build ios --release
+
+cd ios
+fastlane release