Add styles to nav collapse button

[mnicole]

.gds-nav__side--collapse-wrapper {
z-index: 100;
position: absolute;
background: transparent;
border-left: 2px solid transparent;
top: 0;
right: -1.5rem;
height: 100%;
width: 1.5rem;
transition: border;
}
.gds-nav__side--collapse-button {
opacity: 1;
position: absolute;
top: 3rem;
left: -0.75rem;
width: 1.25rem;
height: 1.25rem;
z-index: 10000;
border: none;
cursor: pointer;
background: #fff;
outline: none;
border-radius: 100%;
text-align: center;
color: #949494;
transition: opacity;
box-shadow: 1px 1px 4px 1px #009fc570;
}