feat: add default method for Strings and Numbers

[ftonato]

Description

We would like to be able to have a default value for Strings and Numbers when we receive a Falsy value.

const schema = Nope.string().default('default-value-trim').trim() // 'default-value-trim'

See #641

[github-actions[bot]]

Size Change: +27 B (0%)

Total Size: 5.65 kB

Filename	Size	Change
./lib/umd/index.js	5.65 kB	+27 B (0%)

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