Add substrCount() to Stringable

[pedzed]

The method substrCount is missing and my suggestion is to add it in.

Example

Str::of('abc abc')->substrCount('a');

Expected

2

Actual

Method Illuminate\Support\Stringable::substrCount does not exist.

Stringable::substr() exists and it would be nice to also have Stringable::substrCount().

Related: https://www.php.net/manual/en/function.substr-count.php

[crissto]

Hey @pedzed!
Thanks for the suggestion. This was a nice little problem to be my first contribution to the laravel/framework.