setup formatting for swiftui code

.swiftformat

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+# Formatting Options
+--indent 2
+--maxwidth 100
+--wrapparameters afterfirst
+--disable wrapMultilineStatementBraces

format-swift.sh

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+#!/bin/bash
+
+swiftformat ./FirebaseSwiftUI
+
+swiftformat ./samples/swiftui/FirebaseSwiftUIExample