docs: update .swift-format to Point-Free style (2 spaces)

Change indentation from 4 spaces to 2 spaces to comply with
README standardization checklist requiring Point-Free style.

Author: coenttb

.swift-format

@@ -5,7 +5,7 @@
   "indentConditionalCompilationBlocks" : true,
   "indentSwitchCaseLabels" : false,
   "indentation" : {
-    "spaces" : 4
+    "spaces" : 2
   },
   "lineBreakAroundMultilineExpressionChainComponents" : false,
   "lineBreakBeforeControlFlowKeywords" : false,