Use this to add an operator to append items to sequences, ie: `collection += item`

RangeReplaceableCollectionOperators.swift

extension RangeReplaceableCollection {
    static func += (collection: inout Self, element: Element) {
        collection.append(element)
    }

    static func += (collection: inout Self, element: Element?) {
        if let element = element {
            collection.append(element)
        }
    }
}

extension RangeReplaceableCollection where Element: Equatable {
    static func -= (collection: inout Self, element: Element) {
        if let index = collection.firstIndex(of: element) {
            collection.remove(at: index)
        }
    }

    static func -= (collection: inout Self, element: Element?) {
        if let element = element, let index = collection.firstIndex(of: element) {
            collection.remove(at: index)
        }
    }
}