Fix: isCurrency symbol validator regex

[islasjuanp]

Some of the currency symbols starts with letters. For example:

• Brazil Real R$
• Dominican Republic Peso RD$

For those cases, the RegExp pattern created to validate the currency simbol is not valid:

Generated regex:

 -?(\R$) ?(0|[1-9]\d*|[1-9]\d{0,2}(\,\d{3})*)?(\.(\d{2}))?

Expected regex:

-?(R\$) ?(0|[1-9]\d*|[1-9]\d{0,2}(\.\d{3})*)?(\,(\d{2}))?

Resolves #1292

[profnandaa]

LGTM

[profnandaa]

Thanks for your contribution! 🎉