docs: update the README

Co-authored-by: Athan <[email protected]>
Signed-off-by: Karan Anand <[email protected]>

Author: anandkaranubc

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

@@ -214,7 +214,7 @@ The `continuity` parameter may be one of the following values:
 -   `STDLIB_BASE_HEAVISIDE_CONTINUITY_RIGHT_CONTINUOUS`: if `x == 0`, the function returns `1.0`.
 -   `STDLIB_BASE_HEAVISIDE_CONTINUITY_DISCONTINUOUS`: if `x == 0`, the function returns `NaN`.
 
-If not provided a valid `continuity` parameter, the function returns `NaN` for `x == 0`, behaving like the discontinuous case.
+If provided a `continuity` argument which is not one of the enumeration constants listed above, the function returns `NaN` for `x == 0`, behaving like the discontinuous case.
 
 ```c
 double stdlib_base_heaviside( const double x, const STDLIB_BASE_HEAVISIDE_CONTINUITY continuity );