Add ESLint to maintain code style. Add pre-commit hook to lint prior.

ESLint is used with the standard react plugin. It detects all kinds of
issues ranging from misspells, indentation, variable-naming, etc.
A pre-commit hook is added to git. Prior commiting, ESlint will run
to validate that everything is OK and the user will have the option
to fix it.

Signed-off-by: Sudhanshu Gautam <me@sudhanshug.com>

src/components/error-snackbar.js

@@ -0,0 +1,68 @@
+import {
+  IconButton,
+  makeStyles,
+  Snackbar,
+  SnackbarContent,
+} from '@material-ui/core';
+import ErrorIcon from '@material-ui/icons/Error';
+import CloseIcon from '@material-ui/icons/Close';
+import React from 'react';
+import PropTypes from 'prop-types';
+
+const SnackBarStyles = makeStyles(theme => ({
+  error: {
+    backgroundColor: theme.palette.error.dark,
+  },
+  message: {
+    display: 'flex',
+    alignItems: 'center',
+  },
+  icon: {
+    marginRight: '20px',
+    fontSize: 20,
+  },
+}));
+
+function ErrorSnackBar({open, closeHandle, errorMessage}) {
+  const classes = SnackBarStyles();
+  return (
+    <Snackbar
+      anchorOrigin={{
+        vertical: 'bottom',
+        horizontal: 'left',
+      }}
+      open={open}
+      autoHideDuration={6000}
+      onClose={closeHandle}
+      ContentProps={{
+        'aria-describedby': 'message-id',
+      }}
+    >
+      <SnackbarContent
+        className={classes.error}
+        aria-describedby="client-snackbar"
+        message={
+          <span id="client-snackbar" className={classes.message}>
+            <ErrorIcon className={classes.icon}/>
+            {errorMessage ||
+                'An unexpected error occurred. Please try again'}
+          </span>
+        }
+        action={[
+          <IconButton key="close" aria-label="Close" color="inherit"
+            onClick={closeHandle}>
+            <CloseIcon/>
+          </IconButton>,
+        ]}
+      />
+    </Snackbar>
+  );
+}
+
+ErrorSnackBar.propTypes = {
+  open: PropTypes.boolean,
+  closeHandle: PropTypes.func,
+  errorMessage: PropTypes.string,
+};
+
+export default ErrorSnackBar;