wip: add nginx-src crate with vendored nginx sources

Fixes: nginx#85

Author: bavshin-f5

.gitmodules

@@ -0,0 +1,4 @@
+[submodule "nginx-src/nginx"]
+	path = nginx-src/nginx
+	url = https://github.com/nginx/nginx.git
+	branch = stable-1.28

Cargo.lock

@@ -1,5 +1,6 @@
 [workspace]
 members = [
+    "nginx-src",
     "nginx-sys",
     "examples",
 ]

Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "nginx-src"
+version = "1028.0.0"
+license = "BSD-2-Clause"
+description = "Source of NGINX"
+keywords = ["nginx", "module", "sys"]
+edition.workspace = true
+homepage.workspace = true
+repository.workspace = true
+rust-version.workspace = true
+
+[dependencies]
+duct = "1"