Set base for settings, add volatile settings for theme and language

Goal is to have a common and reusable base for the settings. Having nice styles and saving preferences is out of scope for now.

Note the conversation page is now the "main page" instead of the account settings.

Change-Id: I328686047d924642ae6781096c9f57308e8fea22
diff --git a/client/src/contexts/CustomThemeProvider.tsx b/client/src/contexts/CustomThemeProvider.tsx
new file mode 100644
index 0000000..a78aefb
--- /dev/null
+++ b/client/src/contexts/CustomThemeProvider.tsx
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2022 Savoir-faire Linux Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public
+ * License along with this program.  If not, see
+ * <https://www.gnu.org/licenses/>.
+ */
+import { PaletteMode } from '@mui/material';
+import { ThemeProvider } from '@mui/material/styles';
+import { createContext, useCallback, useEffect, useMemo, useState } from 'react';
+
+import { buildDefaultTheme } from '../themes/Default';
+import { WithChildren } from '../utils/utils';
+
+interface ICustomThemeContext {
+  mode: PaletteMode;
+  toggleMode: () => void;
+}
+
+export const CustomThemeContext = createContext<ICustomThemeContext>(undefined!);
+
+export default ({ children }: WithChildren) => {
+  const [mode, setMode] = useState<PaletteMode>('light');
+
+  useEffect(() => {
+    const browserIsDark = window.matchMedia('(prefers-color-scheme: dark)').matches;
+    // TODO: Check if account saved a preference and use it
+    setMode(browserIsDark ? 'dark' : 'light');
+  }, []);
+
+  const toggleMode = useCallback(() => setMode((mode) => (mode === 'light' ? 'dark' : 'light')), [setMode]);
+
+  const theme = useMemo(() => buildDefaultTheme(mode), [mode]);
+
+  return (
+    <CustomThemeContext.Provider
+      value={{
+        mode,
+        toggleMode,
+      }}
+    >
+      <ThemeProvider theme={theme}>{children}</ThemeProvider>
+    </CustomThemeContext.Provider>
+  );
+};