chore: add minor docs for interpreter

compiler/noirc_frontend/src/hir/comptime/mod.rs

@@ -1,3 +1,15 @@
+//! The comptime interpreter is used to execute Noir code which is marked to
+//! be executed at compilation time. The main uses for this are:
+//!     - Metaprogramming such as deriving trait implementations
+//!     - Interpreting comptime blocks, attribute functions, and macros
+//!     - Evaluation of globals
+//!
+//! This interpreter is run on the HIR while the program is being resolved and type-checked, and before it is monomorphized. Code written to be run at comptime may
+//! then require additional type hints compared to equivalent non-comptime Noir code.
+//!
+//! For more information on Noir's comptime execution and metaprogramming in general, see the linked page in
+//! the [Noir docs](<https://noir-lang.org/docs/noir/concepts/comptime>)
+
 mod display;
 mod errors;
 mod hir_to_display_ast;