fix(components): remove invalid Button props from HTML (#548)

* fix: don't pass invalid props to Link

* fix: added unit test

* fix: implemented shouldForwardProp

src/components/Button/components/PlainButton/PlainButton.js

@@ -16,6 +16,7 @@
 import React from 'react';
 import styled from '@emotion/styled';
 import { css } from '@emotion/core';
+import isPropValid from '@emotion/is-prop-valid';
 
 import { StyledText } from '../../../Text';
 
@@ -49,10 +50,9 @@ const primaryStyles = ({ theme, primary }) =>
     }
   `;
 
-const ButtonLinkWrapper = styled(StyledText)(
-  baseStyles,
-  primaryStyles
-).withComponent('button');
+const ButtonLinkWrapper = styled(StyledText, {
+  shouldForwardProp: isPropValid
+})(baseStyles, primaryStyles).withComponent('button');
 
 /* eslint-disable react/prop-types */
 const PlainButton = ({ components, href, ...rest }) => {

src/components/Button/components/RegularButton/RegularButton.js

@@ -16,6 +16,7 @@
 import React from 'react';
 import styled from '@emotion/styled';
 import { css } from '@emotion/core';
+import isPropValid from '@emotion/is-prop-valid';
 
 import { textMega, calculatePadding } from '../../../../styles/style-helpers';
 
@@ -215,7 +216,9 @@ const buttonLoadingStyles = ({ isLoading }) =>
     pointer-events: none;
   `;
 
-const ButtonElement = styled('button')`
+const ButtonElement = styled('button', {
+  shouldForwardProp: isPropValid
+})`
   ${baseStyles};
   ${primaryStyles};
   ${sizeStyles};

src/components/Sidebar/components/NavItem/NavItem.js

@@ -17,6 +17,7 @@ import React from 'react';
 import PropTypes from 'prop-types';
 import styled from '@emotion/styled';
 import { css } from '@emotion/core';
+import isPropValid from '@emotion/is-prop-valid';
 
 import { componentsPropType } from '../../../../util/shared-prop-types';
 import NavLabel from '../NavLabel';
@@ -82,13 +83,9 @@ const disabledStyles = ({ theme, disabled }) =>
     }
   `;
 
-const StyledLink = styled.a(
-  baseStyles,
-  hoverStyles,
-  selectedStyles,
-  secondaryStyles,
-  disabledStyles
-);
+const StyledLink = styled('a', {
+  shouldForwardProp: isPropValid
+})(baseStyles, hoverStyles, selectedStyles, secondaryStyles, disabledStyles);
 
 const NavItem = ({
   label,