Update to edition 2021 and resolver 2.

Cargo.toml

@@ -12,11 +12,12 @@ repository = "https://github.com/fusion-engineering/rust-git-version"
 documentation = "https://docs.rs/git-version/"
 keywords = ["git", "version", "build"]
 categories = ["development-tools", "development-tools::build-utils"]
-edition = "2018"
+edition = "2021"
 readme = "README.md"
 
 [dependencies]
 git-version-macro = { version = "=0.3.6", path = "git-version-macro" }
 
 [workspace]
+resolver = "2"
 members = ["git-version-macro"]

git-version-macro/Cargo.toml

@@ -6,7 +6,7 @@ authors = [
 	"Maarten de Vries <[email protected]>",
 	"Mara Bos <[email protected]>",
 ]
-edition = "2018"
+edition = "2021"
 description = "Internal macro crate for git-version."
 repository = "https://github.com/fusion-engineering/rust-git-version"
 keywords = ["git"]

git-version-macro/src/lib.rs

@@ -1,5 +1,3 @@
-extern crate proc_macro;
-
 use proc_macro::TokenStream;
 use proc_macro2::{Span, TokenStream as TokenStream2};
 use quote::{quote, ToTokens};