[RFC]: Add C implementation for `@stdlib/math/base/special/avercos`

[Snehil-Shah]

Description

This RFC proposes adding native C implementation for @stdlib/math/base/special/avercos.

double stdlib_base_avercos( const double x );

Related Issues

#649

Questions

No.

Other

No.

Checklist

• I have read and understood the Code of Conduct.
• Searched for existing issues and pull requests.
• The issue name begins with RFC:.

[Snehil-Shah]

Working on it!