feat: Common component 추가- DropDownButton

+import React from 'react';
+import styled from 'styled-components';
+import { dropdownHeaderColorMap } from '../../lib/styles/palette';
+
+const DropDownBlock = styled.div`
+  margin: 0 auto;
+  float: ${props => props.float || ''};
+`;
+
+const DropDownHeader = styled.button`
+  margin-bottom: 0.8em;
+  padding: 0.4em;
+  box-shadow: 0 2px 3px rgba(0, 0, 0, 0.15);
+  font-weight: 500;
+  font-size: ${props => props.size};
+  border: 2px solid ${props => dropdownHeaderColorMap[props.color].borderColor};
+  color: ${props => dropdownHeaderColorMap[props.color].color};
+  background-color: ${props => dropdownHeaderColorMap[props.color].background};
+  &:hover {
+    background-color: ${props =>
+      dropdownHeaderColorMap[props.color].hoverBackground};
+  }
+`;
+
+const DropDown = ({ children, float, color, size }) => {
+  return (
+    <DropDownBlock float={float} color={color} size={size}>
+      <DropDownHeader color={color} size={size}>
+        {children}
+      </DropDownHeader>
+    </DropDownBlock>
+  );
+};
+
+export default DropDown;