Update README.md

Signed-off-by: Gururaj Gurram <[email protected]>

Author: gururaj1512

lib/node_modules/@stdlib/stats/array/nanstdevtk/README.md

@@ -22,6 +22,8 @@ limitations under the License.
 
 > Calculate the [standard deviation][standard-deviation] of an array ignoring `NaN` values and using a one-pass textbook algorithm.
 
+<section class="intro">
+
 The population [standard deviation][standard-deviation] of a finite size population of size `N` is given by
 
 <!-- <equation class="equation" label="eq:population_standard_deviation" align="center" raw="\sigma = \sqrt{\frac{1}{N} \sum_{i=0}^{N-1} (x_i - \mu)^2}" alt="Equation for the population standard deviation."> -->