Update markup

Author: kgryte

lib/node_modules/@stdlib/math/special/abs/README.md

@@ -62,7 +62,7 @@ var y = abs( -1.0 );
 
 The function accepts the following arguments:
 
--   `x`: input [`ndarray`][@stdlib/ndarray/ctor], array-like object, or number.
+-   **x**: input [`ndarray`][@stdlib/ndarray/ctor], array-like object, or number.
 
 If provided an [`ndarray`][@stdlib/ndarray/ctor] or array-like object, the function computes the [absolute value][absolute-value] for each element and returns an [`ndarray`][@stdlib/ndarray/ctor] having the same shape as `x` and containing element-wise results.