Fix Stack Overflow tag: chart.js (#10520)

README.md

@@ -31,7 +31,7 @@ In case you are looking for the docs of version 2, you will have to specify the
 
 ## Contributing
 
-Instructions on building and testing Chart.js can be found in [the documentation](https://www.chartjs.org/docs/master/developers/contributing.html#building-and-testing). Before submitting an issue or a pull request, please take a moment to look over the [contributing guidelines](https://www.chartjs.org/docs/master/developers/contributing) first. For support, please post questions on [Stack Overflow](https://stackoverflow.com/questions/tagged/chartjs) with the `chartjs` tag.
+Instructions on building and testing Chart.js can be found in [the documentation](https://www.chartjs.org/docs/master/developers/contributing.html#building-and-testing). Before submitting an issue or a pull request, please take a moment to look over the [contributing guidelines](https://www.chartjs.org/docs/master/developers/contributing) first. For support, please post questions on [Stack Overflow](https://stackoverflow.com/questions/tagged/chart.js) with the `chart.js` tag.
 
 ## License