docs: update README with C API documentation

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Author: anandkaranubc

lib/node_modules/@stdlib/stats/base/dists/hypergeometric/variance/README.md

@@ -147,6 +147,106 @@ for ( i = 0; i < 10; i++ ) {
 
 <!-- /.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">
+
+### Usage
+
+```c
+#include "stdlib/stats/base/dists/hypergeometric/variance.h"
+```
+
+#### stdlib_base_dists_hypergeometric_variance( N, K, n )
+
+Returns the variance of a hypergeometric distribution.
+
+```c
+double out = stdlib_base_dists_hypergeometric_variance( 16, 11, 4 );
+// returns ~0.688
+```
+
+The function accepts the following arguments:
+
+-   **N**: `[in] double` population size.
+-   **K**: `[in] double` subpopulation size.
+-   **n**: `[in] double` number of draws.
+
+```c
+double stdlib_base_dists_hypergeometric_variance( const double N, const double K, const double n );
+```
+
+</section>
+
+<!-- /.usage -->
+
+<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="notes">
+
+</section>
+
+<!-- /.notes -->
+
+<!-- C API usage examples. -->
+
+<section class="examples">
+
+### Examples
+
+```c
+#include "stdlib/stats/base/dists/hypergeometric/variance.h"
+#include <stdlib.h>
+#include <stdio.h>
+
+static int random_integer( const int min, const int max ) {
+    return min + rand() % ( max - min + 1 );
+}
+
+int main( void ) {
+    double N;
+    double K;
+    double n;
+    double v;
+    int i;
+
+    for ( i = 0; i < 10; i++ ) {
+        N = random_integer( 10, 100 );
+        K = random_integer( 1, N );
+        n = random_integer( 1, N );
+        v = stdlib_base_dists_hypergeometric_variance( N, K, n );
+
+        printf( "N: %lf, K: %lf, n: %lf, Variance: %lf\n", N, K, n, v );
+    }
+
+    return 0;
+}
+```
+
+</section>
+
+<!-- /.examples -->
+
+</section>
+
+<!-- /.c -->
+
 <!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
 
 <section class="references">