Input-button-name rule does not run on non-lowercase types

The following code returns `inapplicable` when running `input-button-name`. This is because the [rules selector](https://github.com/dequelabs/axe-core/blob/develop/lib/rules/input-button-name.json#L4) is case sensitive so does not match when running against non-lowercase types.

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Start with the case-sensitive selector in lib/rules/input-button-name.json and reproduce the issue using the provided mixed-case input types. Done means input-button-name no longer returns inapplicable for SUBMIT, ImAGE, ResET, or buTTON inputs; then run the relevant rule tests if available.

Written by the indexing model from the issue text.