Enhance low contrast themes with additional colours

For FLUID-6297 we are adding additional low contrast themes based on those from Windows. ( See:  https://docs.google.com/document/d/1choXAocN1z_r1rUi2aeWuTqKIWLSB_1YmxhsIESyucI/edit#heading=h.uqdt18grjypx ) In the next phase these contrast themes should be expanded to include all of the colour options outlined per contrast theme to better identify the key elements like buttons and etc.