Add intro for complex inverse

Author: Planeshifter

lib/node_modules/@stdlib/math/base/special/cinv/README.md

@@ -24,6 +24,12 @@ limitations under the License.
 
 <section class="intro">
 
+The inverse of a non-zero complex number `z = a + bi` is defined as
+
+<!-- <equation class="equation" label="eq:complex_inverse" align="center" raw="{\frac {1}{z}}=\frac{\bar{z}}{z{\bar{z}}} = \frac{a}{a^{2}+b^{2}} - \frac{b}{a^2+b^2}i." alt="Complex Inverse" > -->
+
+<!-- </equation> -->
+
 </section>
 
 <!-- /.intro -->