Started working on a dark theme

...nt/src/components/forms/AssigneesForm/assignees-form.scss

.../components/forms/RequirementsForm/requirements-form.scss

client/src/components/forms/RoleForm/role-form.scss

client/src/components/forms/UserForm/user-form.scss

client/src/components/forms/form.scss

client/src/components/graphs/BarChart/bar-chart.scss

...src/components/graphs/LinearProgress/linear-progress.scss

client/src/components/layout/Page/page.scss

client/src/components/layout/ProjectGrid/project-grid.scss

...src/components/layout/ProjectsSlider/projects-slider.scss

client/src/components/layout/TaskList/task-list.scss

client/src/components/layout/UserList/user-list.scss

client/src/components/navigation/Dropdown/dropdown.scss

client/src/components/navigation/Header/header.scss

client/src/components/navigation/Navigation/navigation.scss

client/src/components/navigation/Sidebar/index.tsx

client/src/components/navigation/Sidebar/sidebar.scss

client/src/components/navigation/Tabs/tabs.scss

client/src/components/ui/Comment/comment.scss

client/src/components/ui/Completion/completion.scss