Convert files in themes/ services/ contexts/ to TS

Convert all Javascript files in `client/src/themes`, `client/src/service`, `client/src/contexts` to Typescript.
Convert SvgIcon, Input, ConversationView, Button components to Typescript

Gitlab #30

Change-Id: I0d0505c28e21c771906edf8d5e7b8ce36126fa64
diff --git a/client/src/App.tsx b/client/src/App.tsx
index b0fd67a..c2f72e4 100644
--- a/client/src/App.tsx
+++ b/client/src/App.tsx
@@ -17,7 +17,7 @@
 import JamiMessenger from './pages/JamiMessenger';
 import SignInPage from './pages/LoginDialog';
 import ServerSetup from './pages/ServerSetup';
-import defaultTheme from './themes/default';
+import defaultTheme from './themes/Default';
 import { ThemeDemonstrator } from './themes/ThemeDemonstrator';
 
 // import { useSelector, useDispatch } from 'react-redux'