Unable to build custom widgets using existing scripts in a MacOS Environment

[maneeshaheshan]

Description:
When following the documentation in [1], the script was not executed properly when running 'npm run dev' command in a MacOS Environment. This also leads to not display any of the widgets in dashboard when trying to add to a dashboard.

The solution is to remove the following line from package.json file before running the dev command and the execute 'npm run dev'.

"postbuild": "cpr ./dist/APIMSample ../../../../dashboard/deployment/web-ui-apps/analytics-dashboard/extensions/widgets/APIMSample -o",

Suggested Labels:
[APIM-3.1.0-GA], [Priority/Highest], [Type/Bug]

Affected Product Version:
APIM 3.1.0 Analytics

OS, DB, other environment details and versions:
MacOS High Sierra

[1] https://apim.docs.wso2.com/en/3.1.0/learn/analytics/creating-custom-widgets-in-analytics-dashboards/