reduced usage of isLocal in favour of checking hoarder.downloadedEmojis

wrote tests to check that, Set checking is 1.5 to 2x faster

StickerSlackTests/StickerSlackTests.swift

@@ -140,4 +140,16 @@ struct PerformanceTests {
 			let _ = hoarder.trie.search(prefix: term)
 		}
 	}
+	
+	@Test func testIsLocal() async throws {
+		for emoji in hoarder.emojis {
+			let x = emoji.isLocal
+		}
+	}
+	
+	@Test func testDownloadedEmojis() async throws {
+		for emoji in hoarder.emojis {
+			let x = hoarder.downloadedEmojis.contains(emoji.name)
+		}
+	}
 }