chore: update dependencies

[jvhoven]

• Removed git add from Husky config as it now warns that it does this by default:

husky > pre-commit (node v12.11.0)
⚠ Some of your tasks use git add command. Please remove it from the config since all modifications made by tasks will be automatically added to the git commit index.

• Modified JarbFieldProps to be in line with the FieldProps type definition from react-final-form.

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For some reason, the tests fail on Node.js v10.16.3, but succeed on Node.js v12.x, I think it's fine to update to v12 since it is LTS as well. I've took the liberty to update the Travis config in this pull request. Let me know if this is alright.

[codecov]

Codecov Report

Merging #6 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff          @@
##           master     #6   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           6      6           
  Lines         197    197           
  Branches       41     41           
=====================================
  Hits          197    197

Impacted Files	Coverage Δ
src/JarbField.tsx	100% <100%> (ø)	⬆️

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[jvhoven]

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