Add helper components for UI

Changes:
- Extracted Copyright from LoginDialog file to its own
- Added some helper components
- Removed unnecessary setup from welcome animation
- Added custom React type for svg element
- Fixed ThemeDemonstrator

GitLab: #12
Change-Id: Ie7158520983dab5c7069f179b6f9531b5106ba85
diff --git a/client/src/components/JamiWelcomeLogo.tsx b/client/src/components/JamiWelcomeLogo.tsx
new file mode 100644
index 0000000..8002aab
--- /dev/null
+++ b/client/src/components/JamiWelcomeLogo.tsx
@@ -0,0 +1,45 @@
+/*
+ * 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 { Box, SxProps, Typography } from '@mui/material';
+
+import { ReactComponent as JamiLogo } from '../icons/jami-logo-icon.svg';
+import { jamiLogoDefaultSize } from '../utils/constants';
+
+interface WelcomeLogoProps {
+  logoWidth?: string;
+  logoHeight?: string;
+  boxSxProps?: SxProps;
+}
+
+export default function JamiWelcomeLogo(props: WelcomeLogoProps) {
+  return (
+    <Box
+      sx={{
+        display: 'flex',
+        alignItems: 'center',
+        justifyContent: 'center',
+        textAlign: 'center',
+        flexDirection: 'column',
+        ...props.boxSxProps,
+      }}
+    >
+      <JamiLogo width={props.logoWidth ?? jamiLogoDefaultSize} height={props.logoHeight ?? jamiLogoDefaultSize} />
+      <Typography variant="h1">Welcome to Jami!</Typography>
+    </Box>
+  );
+}