Add Cargo metadata

Cargo.toml

@@ -4,6 +4,25 @@ version = "0.1.0"
 authors = ["Lukas Kalbertodt <lukas.kalbertodt@gmail.com>"]
 edition = "2018"
 
+description = """
+Parse and inspect Rust literals (i.e. tokens in the Rust programming language
+representing fixed values). Particularly useful for proc macros, but can also
+be used outside of a proc-macro context.
+"""
+documentation = "https://docs.rs/litrs/"
+repository = "https://github.com/LukasKalbertodt/litrs/"
+readme = "README.md"
+license = "MIT/Apache-2.0"
+
+keywords = ["literal", "parsing", "proc-macro", "type", "procedural"]
+categories = [
+    "development-tools::procedural-macro-helpers",
+    "parser-implementations",
+    "development-tools::build-utils",
+]
+exclude = [".github"]
+
+
 [features]
 default = ["proc-macro", "proc-macro2"]
 proc-macro = []