style: add positive attribute to submit buttons (close #113)

web/src/pages/User/AddUser.js

@@ -65,7 +65,7 @@ const AddUser = () => {
               required
             />
           </Form.Field>
-          <Button type={'submit'} onClick={submit}>
+          <Button positive type={'submit'} onClick={submit}>
             提交
           </Button>
         </Form>

web/src/pages/User/EditUser.js

@@ -142,7 +142,7 @@ const EditUser = () => {
               readOnly
             />
           </Form.Field>
-          <Button onClick={submit}>提交</Button>
+          <Button positive onClick={submit}>提交</Button>
         </Form>
       </Segment>
     </>