Fixes doc links for procedural crate (#5023)

This PR fixes the documentation for FRAME Macros when pointed from
`polkadot_sdk_docs` crate. This is achieved by referring to the examples
in the `procedural` crate, embedded via `docify`.

---------

Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>

substrate/frame/support/procedural/Cargo.toml

@@ -19,6 +19,7 @@ proc-macro = true
 
 [dependencies]
 derive-syn-parse = { workspace = true }
+docify = { workspace = true }
 Inflector = { workspace = true }
 cfg-expr = { workspace = true }
 itertools = { workspace = true }
@@ -32,14 +33,42 @@ expander = { workspace = true }
 sp-crypto-hashing = { workspace = true }
 
 [dev-dependencies]
+codec = { features = [
+	"derive",
+	"max-encoded-len",
+], workspace = true }
 regex = { workspace = true }
+sp-metadata-ir = { workspace = true }
+scale-info = { features = ["derive"], workspace = true }
+sp-core = { workspace = true }
+sp-io = { workspace = true }
+sp-runtime = { features = [
+	"serde",
+], workspace = true }
+frame-system = { workspace = true }
+frame-support = { workspace = true }
+pretty_assertions = { workspace = true }
+static_assertions = { workspace = true }
 
 [features]
 default = ["std"]
-std = ["sp-crypto-hashing/std"]
+std = [
+	"codec/std",
+	"frame-support/std",
+	"frame-system/std",
+	"scale-info/std",
+	"sp-core/std",
+	"sp-crypto-hashing/std",
+	"sp-io/std",
+	"sp-metadata-ir/std",
+	"sp-runtime/std",
+]
 no-metadata-docs = []
 experimental = []
 # Generate impl-trait for tuples with the given number of tuples. Will be needed as the number of
 # pallets in a runtime grows. Does increase the compile time!
 tuples-96 = []
 tuples-128 = []
+
+[[example]]
+name = "proc_main"

substrate/frame/support/src/tests/inject_runtime_type.rs → substrate/frame/support/procedural/examples/proc_main/inject_runtime_type.rs

@@ -15,8 +15,11 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#[cfg(test)]
 use super::{Config, Runtime};
+#[cfg(test)]
 use crate::{derive_impl, pallet_prelude::inject_runtime_type};
+#[cfg(test)]
 use static_assertions::assert_type_eq_all;
 
 #[docify::export]