add static title for required mark

Author: msmx-mnakagawa

src/scripts/CheckboxGroup.tsx

@@ -112,7 +112,11 @@ export const CheckboxGroup = createFC<
         onChange={onChange}
       >
         <legend className='slds-form-element__label'>
-          {required ? <abbr className='slds-required'>*</abbr> : undefined}
+          {required ? (
+            <abbr className='slds-required' title='required'>
+              *
+            </abbr>
+          ) : undefined}
           {label}
         </legend>
         <div className='slds-form-element__control' ref={controlElRef}>

src/scripts/FormElement.tsx

@@ -100,7 +100,11 @@ export const FormElement = createFC<
               htmlFor={id}
               onClick={id ? undefined : onClickLabel}
             >
-              {required ? <abbr className='slds-required'>*</abbr> : undefined}
+              {required ? (
+                <abbr className='slds-required' title='required'>
+                  *
+                </abbr>
+              ) : undefined}
               {label}
             </label>
           ) : null}

src/scripts/RadioGroup.tsx

@@ -90,7 +90,11 @@ export const RadioGroup = createFC<RadioGroupProps, { isFormElement: boolean }>(
         {...rprops}
       >
         <legend className='slds-form-element__label'>
-          {required ? <abbr className='slds-required'>*</abbr> : undefined}
+          {required ? (
+            <abbr className='slds-required' title='required'>
+              *
+            </abbr>
+          ) : undefined}
           {label}
         </legend>
         <div className='slds-form-element__control'>