Fix documentation (validation option, slider example)

[2called-chaos]

Describe the change

Fixes documentation in Readme

Why are we doing this?

For Sparta!

Benefits

Functioning examples

Drawbacks

No puzzle for developers

Requirements

Put an X between brackets on each line if you have done the item:
[] Tests written & passing locally? (there is in fact no test using the validation option opposed to the #validate method. should I modify one of the existing or add a new test?)
[X] Code style checked?
[X] Rebased with master branch?
[X] Documentation updated?

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As per options.fetch(:validation)

The other example lead to incomplete format specifier; use %% (double %) instead

[coveralls]

Coverage decreased (-0.2%) to 96.991% when pulling 5c327b9 on 2called-chaos:master into 65187af on piotrmurach:master.

[coveralls]

Coverage decreased (-0.1%) to 97.025% when pulling fed650a on 2called-chaos:master into 65187af on piotrmurach:master.

[piotrmurach]

Hi Sven,

Thanks for this PR! I think this is a bug that you found here rather than document fix! The DSL method is called validate and the key should also match that and be called :validate. Could you please change this PR to only include the slider readme fix. If you have time and want to help I would appreciate fixing the option with a test confirming the fix.

[piotrmurach]

Thanks ❤️