the fix for the boolean uppercase-value attribute validation

[citysitesdev]

Оften the logical value of the attribute is written with a capital letter, for example, Truе. However, the validator in "ymlparser" does not pass such values. I suggest the following improvement to be written in /src/Offer/AOffer.php

[vsdm]

What to do with "tRue"?
I think it should be like this
if ($this->store !== null && strtolower($this->store) !== 'true' && strtolower($this->store) !== 'false')

[shaperman]

What to do with "tRue"?

I believe that in this context "tRue" is a mistake and the result of validation should be negative.