docs: align _tools/pkgs/namespace-deps with namespace JSDoc convention

Added `@example` blocks to the public `namespaceDeps` function's
JSDoc (present in 92% of `_tools/pkgs` siblings, 23/25). Examples
are lifted from the package README's existing usage snippets; no
behavioral or signature changes.

https://claude.ai/code/session_018TZhAvyL3P8FYzhGm4G1LH

Author: claude

lib/node_modules/@stdlib/_tools/pkgs/namespace-deps/lib/main.js

@@ -60,6 +60,18 @@ function ascending( a, b ) {
 * @param {number} [options.level=1] - dependency level
 * @throws {TypeError} first argument must be a string
 * @returns {(StringArray|EmptyArray)} dependencies
+*
+* @example
+* var deps = namespaceDeps( '@stdlib/assert' );
+* // returns [...]
+*
+* @example
+* var opts = {
+*     'dev': true
+* };
+*
+* var devDeps = namespaceDeps( '@stdlib/assert', opts );
+* // returns [...]
 */
 function namespaceDeps( pkg, options ) {
 	var opts;