adds ability to set custom validator on Text and Number inputs

[vesper8]

nothing special here, just added the same functionality currently available on the Password field to the Number and Text fields

[codecov-io]

Codecov Report

Merging #177 into master will decrease coverage by 1.01%.
The diff coverage is 12.5%.

@@             Coverage Diff              @@
##             master     #177      +/-   ##
============================================
- Coverage     97.26%   96.24%   -1.02%     
- Complexity      423      429       +6     
============================================
  Files            25       25              
  Lines          1317     1333      +16     
============================================
+ Hits           1281     1283       +2     
- Misses           36       50      +14

Impacted Files	Coverage Δ	Complexity Δ
src/Input/Text.php	79.41% <12.5%> (-20.59%)	14 <1> (+3)
src/Input/Number.php	81.57% <12.5%> (-18.43%)	16 <1> (+3)

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[AydinHassan]

Thanks!