misc: Add more categories to Cargo.toml

Author: Serial-ATA

Cargo.toml

@@ -7,7 +7,7 @@ license     = "MIT OR Apache-2.0"
 description = "Audio metadata library"
 repository  = "https://github.com/Serial-ATA/lofty-rs"
 keywords    = ["tags", "audio", "metadata", "id3", "vorbis"]
-categories  = ["multimedia::audio"]
+categories  = ["multimedia", "multimedia::audio", "parser-implementations"]
 readme      = "README.md"
 include     = ["src", "Cargo.toml", "LICENSE-APACHE", "LICENSE-MIT", "benches", "SUPPORTED_FORMATS.md"]