fix(logpdf): fix README C section structure to match stdlib conventions

Signed-off-by: Kamal Singh Rautela <e22cseu1624@bennett.edu.in>

Author: rautelaKamal

lib/node_modules/@stdlib/stats/base/dists/lognormal/logpdf/README.md

@@ -134,10 +134,24 @@ logEachMap( 'x: %0.4f, µ: %0.4f, σ: %0.4f, ln(f(x;µ,σ)): %0.4f', x, mu, sigm
 
 <!-- /.examples -->
 
-<!-- C usage documentation. -->
+<!-- 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">
 
 ### Usage
@@ -177,23 +191,36 @@ double stdlib_base_dists_lognormal_logpdf( const double x, const double mu, cons
 
 <!-- /.notes -->
 
+<!-- C API usage examples. -->
+
 <section class="examples">
 
 ### Examples
 
 ```c
 #include "stdlib/stats/base/dists/lognormal/logpdf.h"
+#include <stdlib.h>
 #include <stdio.h>
 
+static double random_uniform( const double min, const double max ) {
+    double v = (double)rand() / ( (double)RAND_MAX + 1.0 );
+    return min + ( v*(max-min) );
+}
+
 int main( void ) {
+    double x;
+    double mu;
+    double sigma;
     double y;
     int i;
 
     for ( i = 0; i < 25; i++ ) {
-        y = stdlib_base_dists_lognormal_logpdf( (double)i, 0.0, 1.0 );
-        printf( "x: %d, logpdf: %lf\n", i, y );
+        x = random_uniform( 0.0, 100.0 );
+        mu = random_uniform( -10.0, 10.0 );
+        sigma = random_uniform( 0.1, 10.0 );
+        y = stdlib_base_dists_lognormal_logpdf( x, mu, sigma );
+        printf( "x: %lf, mu: %lf, sigma: %lf, ln(f(x;mu,sigma)): %lf\n", x, mu, sigma, y );
     }
-    return 0;
 }
 ```