Allow non-string values as context.

[garg3133]

This PR removes the const el = document.querySelector(selector); statement for the following reasons:

• axe-core's context argument is really powerful and supports the input in a lot of varied formats, but having the above statement limits the first argument of .axeRun() command to only accept string input.
• We don't need to resolve the DOM nodes from the selector ourselves as that can be handled by Axe-core itself.
• Having document.querySelector() limits the axe check to only one matching DOM node and that's it. So, if we want to check some elements for accessibility that have the same class name, it will always choose the first matching node only and the other matching nodes will remain untested. Also, to check for multiple elements with unique CSS selectors, we would need to run .axeRun() command multiple times as we cannot pass all the selectors once (which is supported by axe-core by separating multiple CSS selectors by ,).

Since I am unaware, is there a reason why the above-mentioned statement was included in the code in the first place?

[reallymello]

Tests still passing omitting the query selector which adds better functionality as you mentioned. Thanks.