docs(gmeta): add documentation for gmeta crate (#2761)

gmeta/Cargo.toml

@@ -10,5 +10,10 @@ hex = { workspace = true, features = ["alloc"] }
 gmeta-codegen = { path = "codegen", optional = true }
 derive_more.workspace = true
 
+[dev-dependencies]
+gear-wasm-builder.workspace = true
+gstd.workspace = true
+parity-scale-codec.workspace = true
+
 [features]
 codegen = ["gmeta-codegen"]

gmeta/codegen/src/lib.rs

@@ -1,3 +1,21 @@
+// This file is part of Gear.
+
+// Copyright (C) 2022-2023 Gear Technologies Inc.
+// SPDX-License-Identifier: GPL-3.0-or-later WITH Classpath-exception-2.0
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with this program. If not, see <https://www.gnu.org/licenses/>.
+
 use proc_macro::TokenStream;
 use quote::{quote, ToTokens};
 use std::{borrow::Borrow, fmt::Display, iter};
@@ -55,6 +73,7 @@ fn validate_if_has_no_attributes(
 /// Generates metawasm functions.
 ///
 /// An example of the expected structure:
+///
 /// ```
 /// use gstd::prelude::*;
 ///
@@ -101,7 +120,7 @@ fn validate_if_has_no_attributes(
 /// `State` identifier. The type for which `State` will be an alias **must**
 /// implement [`Decode`] trait.
 ///
-/// Usually the state type should be imported from the implemented associative
+/// Usually the state type should be imported from the implemented associated
 /// [`Metadata::State`](../gmeta/trait.Metadata.html#associatedtype.State) type
 /// from the contract's `io` crate.
 ///