Improve help page - switch affiliation

Add a section in the help page:

• title: "How to switch between affiliations to see data from previous projects?"

• text: If you have multiple accounts with different affiliations in the User Portal, these affiliations are automatically reflected in the Data Portal. To switch between affiliations in the Data Portal, click on the menu under your login name and select the desired affiliation. The data associated with each affiliation will be displayed accordingly.