feat: [sc-741] add helper for map with lock (#22)

* feat: [sc-741] add helper for dictionary with lock

Sources/ConcurrencyHelpers/DictionaryWithLock.swift

@@ -0,0 +1,20 @@
+public struct DictionaryWithLock<K: Hashable, V> {
+    var lock: ConcurrencyHelpers.Lock = .init()
+    var map: [K: V] = [:]
+
+    public subscript(key: K) -> V? {
+        get {
+            lock.withLock {
+                guard let value = map[key] else {
+                    return nil
+                }
+                return value
+            }
+        }
+        set {
+            lock.withLock {
+                map[key] = newValue
+            }
+        }
+    }
+}