Add deprecated feature and migrate string_proc to just_fmt

- Add `deprecated` feature flag to Cargo.toml
- Gate `string_proc` module behind both `deprecated` and `string_proc`
  features
- Replace internal `string_proc` dependency with `just_fmt` crate in
  constants macros
- Mark all `string_proc` modules as deprecated with migration
  instructions
- Remove `string_proc` dependency from sheet system

1 files changed, 1 insertions, 1 deletions

diff --git a/systems/_constants/macros/src/lib.rs b/systems/_constants/macros/src/lib.rs
index f6cf945..2d3f255 100644
--- a/systems/_constants/macros/src/lib.rs
+++ b/systems/_constants/macros/src/lib.rs
@@ -1,6 +1,6 @@
+use just_fmt::pascal_case;
 use proc_macro::TokenStream;
 use quote::quote;
-use string_proc::pascal_case;
 use syn::{Expr, ExprLit, Ident, Item, ItemMod, Lit, LitStr, parse_macro_input};
 
 #[proc_macro_attribute]