fix #105 - validate all strings

[acao]

any string that is not empty, including whitespace strings, should validate?

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: b1d6a009d949deee0267f2d570be3c7417fea3e2

The changes in this PR will be included in the next version bump.

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| Name | Type | | ---------------------- | ----- | | codemirror-json-schema | Patch |

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[imolorhe]

@rookie-luochao what version are you using?

[rookie-luochao]

@rookie-luochao what version are you using?

0.7.6