CHMOD - Add MASK

[ruxlin]

trafficstars

Describe the solution you'd like I know it is rather trivial for the learned, but having a mask conversion in another box would be a great addition imo, or simply add a text to suggest that if you wish to calculate the mask, just -7 from each of the numerals in the CHMOD calculator.

Additional context Add any other context about the feature request here.

[webysther]

https://chmod-calculator.com/

I miss a input to put the file permission

[sharevb]

Will prepare a PR

[sharevb]

Hi @webysther, @ruxlin an @CorentinTh, implemented in #964