[M5+] add documentary Cargoxx.toml + fix LinkdbUnknownPackage hint formatting

Cargoxx.toml

@@ -0,0 +1,15 @@
+[package]
+name = "cargoxx"
+version = "0.1.0"
+edition = "cpp23"
+license = "MIT"
+
+[dependencies]
+sqlite3 = "*"
+reproc = "*"
+
+[dev-dependencies]
+catch2 = "*"
+
+[build]
+warnings_as_errors = false

src/linkdb/database.cpp

@@ -69,8 +69,9 @@ auto Database::resolve(const std::string& package, const std::string& version,
     return std::unexpected(util::Error{
         util::ErrorCode::LinkdbUnknownPackage,
         std::format("package '{}' has no known CMake link recipe", package),
-        "run `cargoxx add {0}` to discover and verify a recipe via the resolver, "
-        "or add a manual recipe via `cargoxx linkdb add`",
+        std::format("run `cargoxx add {}` to discover and verify a recipe via "
+                    "the resolver, or add a manual recipe via `cargoxx linkdb add`",
+                    package),
         std::nullopt, std::nullopt,
     });
 }