m-form-success 
Displays a message when the form is successfully submitted. Can only be used inside the m-form tag.
TIP
Template expressions wrapped in double square brackets are supported.
Example 
html
<m-form>
    <m-form-success>Thanks you for submit<br /> [[success]]</m-form-success>
</m-form>html
<m-form>
    <m-form-success></m-form-success>
</m-form>