Adding link for inventree demo (#3613)

README.md

@@ -1376,7 +1376,7 @@ _See also: [awesome-sysadmin/IT Asset Management](https://github.com/awesome-fos
 - [Hub20](https://hub20.io/) - A self-hosted payment processor for Ethereum and ERC20 Tokens. ([Source Code](https://gitlab.com/mushroomlabs/hub20/)) `AGPL-3.0` `Docker/Python`
 - [IHateMoney](https://ihatemoney.org/) - Manage your shared expenses, easily. ([Demo](https://ihatemoney.org/demo/), [Source Code](https://github.com/spiral-project/ihatemoney)) `BSD-3-Clause` `Docker/Python`
 - [Inventaire](https://inventaire.io/welcome) - Collaborative resources mapper project, while yet only focused on exploring books mapping with wikidata and ISBNs. ([Source Code](https://github.com/inventaire/inventaire)) `AGPL-3.0` `Nodejs`
-- [Inventree](https://inventree.readthedocs.io/en/latest/) - InvenTree is an open-source inventory management system which provides intuitive parts management and stock control. ([Source Code](https://github.com/inventree/InvenTree)) `MIT` `Python`
+- [Inventree](https://inventree.readthedocs.io/en/latest/) - InvenTree is an open-source inventory management system which provides intuitive parts management and stock control. ([Demo](https://inventree.org/demo), [Source Code](https://github.com/inventree/InvenTree)) `MIT` `Python`
 - [Invoice Ninja](https://www.invoiceninja.org/) - Powerful tool to invoice clients online. ([Demo](https://app.invoiceninja.com/invoices/create), [Source Code](https://github.com/invoiceninja/invoiceninja)) `AAL` `PHP`
 - [InvoicePlane](https://github.com/InvoicePlane/InvoicePlane) - Manage quotes, invoices, payments and customers for your small business. `MIT` `PHP`
 - [Kresus](https://kresus.org/) - Open source personal finance manager. ([Demo](https://kresus.org/en/demo.html), [Source Code](https://github.com/kresusapp/kresus)) `MIT` `Nodejs`