Add routing for call page

Enable buttons to start a call.
Improve ConversationListItem context menu layout.
Move calling buttons from `Button.tsx` to `CallButtons.tsx`.
Add CallProvider

GitLab: #78
Change-Id: I921aa11383bf39fae18e59b01afb00dc66b0d5e6
diff --git a/client/src/utils/utils.ts b/client/src/utils/utils.ts
index 8f2f1cb..ffe37a4 100644
--- a/client/src/utils/utils.ts
+++ b/client/src/utils/utils.ts
@@ -15,8 +15,10 @@
  * License along with this program.  If not, see
  * <https://www.gnu.org/licenses/>.
  */
-import { ReactNode } from 'react';
+import { Dispatch, ReactNode, SetStateAction } from 'react';
 
 export type WithChildren = {
   children: ReactNode;
 };
+
+export type SetState<T> = Dispatch<SetStateAction<T>>;