fix: add intro section with Apery's constant formula per convention

Author: Amansingh0807

lib/node_modules/@stdlib/constants/float16/apery/README.md

@@ -22,6 +22,24 @@ limitations under the License.
 
 > [Apéry's constant][apery-constant].
 
+<section class="intro">
+
+[Apéry's constant][apery-constant] is defined as
+
+<!-- <equation class="equation" label="eq:apery_constant" align="center" raw="\zeta(3) = \sum_{n=1}^\infty \frac{1}{n^3} = \lim_{n\to\infty} \biggl(\frac{1}{1^3} + \frac{1}{2^3} + \cdots + \frac{1}{n^3}\biggr)" alt="Apéry's constant"> -->
+
+```math
+\zeta(3) = \sum_{n=1}^\infty \frac{1}{n^3} = \lim_{n\to\infty} \biggl(\frac{1}{1^3} + \frac{1}{2^3} + \cdots + \frac{1}{n^3}\biggr)
+```
+
+<!-- </equation> -->
+
+where `ζ(s)` is the Riemann zeta function.
+
+</section>
+
+<!-- /.intro -->
+
 <section class="usage">
 
 ## Usage
@@ -32,7 +50,7 @@ var FLOAT16_APERY = require( '@stdlib/constants/float16/apery' );
 
 #### FLOAT16_APERY
 
-[Apéry's constant][apery-constant], the value of the Riemann zeta function ζ(3), represented in half-precision floating-point format.
+[Apéry's constant][apery-constant].
 
 ```javascript
 var bool = ( FLOAT16_APERY === 1.2021484375 );