Application crashes if there are two environment variables with same name, differing only in case

[Tyrrrz]

Original issue: Tyrrrz/DiscordChatExporter#342

[Tyrrrz]

Should be an easy fix. The offending lines are here:

CliFx/CliFx/CliApplication.cs

Lines 221 to 223 in b491818

	var environmentVariables = Environment.GetEnvironmentVariables()
	.Cast<DictionaryEntry>()
	.ToDictionary(e => (string) e.Key, e => (string) e.Value, StringComparer.OrdinalIgnoreCase);