docs: add C API documentation and usage examples for exponential mode

Author: sethdivyansh

lib/node_modules/@stdlib/stats/base/dists/exponential/mode/README.md

@@ -114,6 +114,96 @@ 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/exponential/mode.h"
+```
+
+#### stdlib_base_dists_exponential_mode( λ )
+
+Returns the [mode][mode] of an [exponential][exponential-distribution] distribution with rate parameter `λ`.
+
+```c
+double out = stdlib_base_dists_exponential_mode( 0.5 );
+// returns 0.0
+```
+
+The function accepts the following arguments:
+
+-   **λ**: `[in] double` mode parameter.
+
+```c
+double stdlib_base_dists_exponential_mode( const double lambda );
+```
+
+</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/exponential/mode.h"
+#include <stdlib.h>
+#include <stdio.h>
+
+int main( void ) {
+    double lambda;
+    double v;
+    int i;
+
+    for ( i = 0; i < 10; i++ ) {
+        lambda = 20.0 * (double)rand() / ( (double)RAND_MAX + 1.0 );
+        v = stdlib_base_dists_exponential_mode( lambda );
+        printf( "λ: %lf , E(X;λ): %lf\n", lambda , v );
+    }
+}
+```
+
+</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">

lib/node_modules/@stdlib/stats/base/dists/exponential/mode/package.json

@@ -14,11 +14,14 @@
     }
   ],
   "main": "./lib",
+  "gypfile": true,
   "directories": {
     "benchmark": "./benchmark",
     "doc": "./docs",
     "example": "./examples",
+    "include": "./include",
     "lib": "./lib",
+    "src": "./src",
     "test": "./test"
   },
   "types": "./docs/types",