Improve Accessibility of Text Inputs

[dev-nicolaos]

Text inputs within the GitHub configuration UI do not have accessible labels associated with them, instead relying on the placeholder attribute to provide a name. placeholders are poor substitutes for visible labels because they disappear once a user has entered a value.

For reference: https://developer.mozilla.org/en-US/docs/Web/Accessibility/Understanding_WCAG/Text_labels_and_names#form_elements_must_be_labeled