[optimization] create single instance of URLSession instead of initializing one every request

[Tohr01]

LeagueDeathTimer/LeagueDeathTimer/api/urlsessiondelegate.swift

Line 23 in 0f5e2ae

guard let (data, _) = try? await URLSession(configuration: .default, delegate: CertIgnoreURLSessionDelegate(), delegateQueue: .main).data(for: urlRequest),