fix(helper-text): Support deprecated exports and selectors (#1625)
fix(helper-text): Support deprecated exports and selectors (#1625)

Support for deprecated exports and selectors, so we avoid a breaking change for the time being.

`mdc-text-field-helper-text, [mdcTextFieldHelperText], [mdcSelectHelperText]`
trimox/angular-mdc-web,trimox/angular-mdc-web