Add new crate leon-macros that provide template! with identical syntax as runtime parsing (#946)

`leon_macros::template!` can parse template at compile-time.
It accepts a utf-8 string literal and uses `leon` internally to parse it, then generate code that evaluates to `Template<'static>`.

 - Exclude fuzz from crate leon when publishing
 - Impl fn-like proc-macro `leon_macros::template!`
 - Add dep `leon-macros` to binstalk
 - Use `leon_macros::template!` in `binstalk::fetchers::gh_crate_meta::hosting`
 - Add doc for `leon-macros` in `leon`
 - Improve `std::fmt::Display` impl for `leon::ParseError`
 - Fixed broken infra link in leon

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

Cargo.lock

@@ -231,6 +231,7 @@ dependencies = [
  "itertools",
  "jobslot",
  "leon",
+ "leon-macros",
  "maybe-owned",
  "miette",
  "normalize-path",
@@ -1338,6 +1339,16 @@ dependencies = [
  "tinytemplate",
 ]
 
+[[package]]
+name = "leon-macros"
+version = "0.0.0"
+dependencies = [
+ "leon",
+ "proc-macro2",
+ "quote",
+ "syn 2.0.15",
+]
+
 [[package]]
 name = "libc"
 version = "0.2.141"