Add extensions for Collection, Array, and Set

Sources/AppFoundations/Extensions/Array/Array+SafeAccess.swift

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+//
+//  Array+SafeAccess.swift
+//  
+//
+//  Created by Mark DiFranco on 2023-09-01.
+//
+
+import Foundation
+
+public extension Array {
+
+    /// Returns the element at `index`, or nil if `index` is out of the bounds.
+    /// - parameter index: The index of the element to access.
+    /// - returns: The element at the given index, or `nil` if the index is out of bounds.
+    func safeAccess(at index: UInt) -> Element? {
+        guard count > index else { return nil }
+
+        return self[Int(index)]
+    }
+}

Sources/AppFoundations/Extensions/Collection/Collection+Checks.swift

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+//
+//  Collection+Checks.swift
+//  
+//
+//  Created by Mark DiFranco on 2023-09-01.
+//
+
+import Foundation
+
+public extension Collection {
+
+    /// Whether `self` is empty or not.
+    /// - returns: `true` if `self` is not empty, `false` otherwise.
+    var isNotEmpty: Bool { !isEmpty }
+}

Sources/AppFoundations/Extensions/Collection/Collection+Set.swift

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+//
+//  Collection+Set.swift
+//  
+//
+//  Created by Mark DiFranco on 2023-09-01.
+//
+
+import Foundation
+
+public extension Collection where Element: Hashable {
+
+    /// Creates a ``Set`` from the elements in `self`.
+    func asSet() -> Set<Element> {
+        Set(self)
+    }
+}

Sources/AppFoundations/Extensions/Set/Set+Membership.swift

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+//
+//  Set+Membership.swift
+//  
+//
+//  Created by Mark DiFranco on 2023-09-01.
+//
+
+import Foundation
+
+public extension Set {
+
+    /// Returns this ``Set`` with `element` inserted.
+    /// - parameter element: The `Element` to insert.
+    /// - returns: This ``Set`` with `element` inserted.
+    func inserting(_ element: Element) -> Self {
+        var mutatedSelf = self
+        mutatedSelf.insert(element)
+        return mutatedSelf
+    }
+
+    /// If the `element` is present in this ``Set``, it is removed. Otherwise, the `element` is inserted.
+    /// - parameter element: The `Element` to insert.
+    mutating func toggleMembership(_ element: Element) {
+        if contains(element) {
+            remove(element)
+        } else {
+            insert(element)
+        }
+    }
+}