Dynamic adjustment of letter spacing when resizing with auto_size_text

[con-cis]

Is your feature request related to a problem? Please describe.
It would be nice if you can also scale the letter spacing depending scale of the text size

Describe the solution you'd like
Dynamic adjustment of letter spacing when resizing with auto_size_text relatively to text size increase

E.G.

minFontSize: 24.0,
minLetterSpacing: 1.0,

maxFontSize: 24.0,
maxLetterSpacing: 1.8,

Describe alternatives you've considered

letterSpacing: MediaQuery.of(context).size.width * 0.005

Version

• Flutter version: [1.5.4]
• auto_size_text version: [1.2.1]