Add hex and float validators

[martijn00]

Connection with issue(s)

Close #???

Connected to #???

Solution description

Screenshots or Videos

To Do

• [x] Read contributing guide
• [x] Check the original issue to confirm it is fully satisfied
• [x] Add solution description to help guide reviewers
• [x] Add unit test to verify new or fixed behaviour
• [x] If apply, add documentation to code properties and package readme

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.09%. Comparing base (da39169) to head (da2debe).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #127 +/- ## ========================================== + Coverage 95.00% 95.09% +0.08% ========================================== Files 92 94 +2 Lines 1002 1020 +18 ========================================== + Hits 952 970 +18 Misses 50 50 ``` | [Flag](https://app.codecov.io/gh/flutter-form-builder-ecosystem/form_builder_validators/pull/127/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flutter-form-builder-ecosystem) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/flutter-form-builder-ecosystem/form_builder_validators/pull/127/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flutter-form-builder-ecosystem) | `95.09% <100.00%> (+0.08%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=flutter-form-builder-ecosystem#carryforward-flags-in-the-pull-request-comment) to find out more.

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.