implementing accessibility

src/App.css

src/App.js

src/Components/Acessibility/ContrastBar.css

src/Components/Acessibility/ContrastBar.js

src/Components/ActivityListItem.js

src/Components/Dropdown.js

src/Components/MenuBar.js

src/Components/Notifications.js

src/Store.js

src/env.js

src/img/OffContrastIcon.png

src/img/OnContrastIcon.png