Add book_bot_macros proc-macro crate

Introduce log_handler attribute macro that injects tracing logs into
handler functions. It extracts user_id from Message (optionally) or
CallbackQuery and logs handler name; falls back to logging handler only.

book_bot_macros/Cargo.toml

@@ -0,0 +1,12 @@
+[package]
+name = "book_bot_macros"
+version = "0.1.0"
+edition = "2021"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+syn = { workspace = true }
+quote = { workspace = true }
+proc-macro2 = { workspace = true }