fix: allow use limit as {String}

[alexander-akait]

Issues

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• Fixes [v0.6.0] ValidationError using limit as {String} #95

[damonbauer]

FWIW it looks like loader-utils does not parse numbers:

?xyz=1 -> { xyz: "1" } // numbers are NOT parsed

https://github.com/webpack/loader-utils#parsequery

[alexander-akait]

@damonbauer we use https://github.com/webpack-contrib/url-loader/blob/master/index.js#L20 if it is string