fix: improve documentation for snanmeanpn function

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Author: 0PrashantYadav0

lib/node_modules/@stdlib/stats/base/snanmeanpn/README.md

@@ -172,6 +172,22 @@ console.log( v );
 
 <!-- /.examples -->
 
+<!-- C interface documentation. -->
+
+* * *
+
+<section class="c">
+
+## C APIs
+
+<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
+
+<section class="intro">
+
+</section>
+
+<!-- /.intro -->
+
 <!-- C usage documentation. -->
 
 <section class="usage">
@@ -273,6 +289,10 @@ int main( void ) {
 
 <!-- /.c -->
 
+<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
+
+<section class="related">
+
 * * *
 
 <section class="references">