Added PropTypes to ItemCounter component.

src/components/ItemCounter/ItemCounter.js

@@ -1,5 +1,6 @@
 import { makeStyles, Typography, useTheme } from '@material-ui/core'
 import React from 'react'
+import PropTypes from "prop-types";
 
 export default function ItemCounter({ filteredItems, totalItems }) {
     const theme = useTheme();
@@ -10,6 +11,20 @@ export default function ItemCounter({ filteredItems, totalItems }) {
     });
     const classes = useStyles();
     return (
-        <Typography classes={{ root: classes.margin }}>{`Showing ${filteredItems} out of ${totalItems}`}</Typography>
+        <Typography classes={{ root: classes.margin }}>
+            {`Showing ${filteredItems} out of ${totalItems}`}
+        </Typography>
     )
 }
+
+ItemCounter.propTypes = {
+	/** The number of filtered items in the table. */
+	"filteredItems": PropTypes.number.isRequired,
+	/** The total number of items in the table */
+	"totalitems": PropTypes.number.isRequired
+};
+
+ItemCounter.defaultProps = {
+    "filteredItems": 0,
+    "totalItems": 0,
+};