feat(runtime): add portable runtime support

req: push/009 req: push/010 req: push/011

examples/cloudflare_do/build.rs

@@ -0,0 +1,10 @@
+fn main() {
+    let templates = std::path::PathBuf::from(
+        std::env::var_os("CARGO_MANIFEST_DIR").expect("Cargo sets CARGO_MANIFEST_DIR"),
+    )
+    .join("templates");
+    hemx_build::app()
+        .template_dir(templates)
+        .run()
+        .expect("compile cloudflare_do hemx surfaces");
+}