Yes Bylla it is supported but in this case you will have PFTT=1(data will be distributed accross both two data sites) and SFTT=0(because in this case the minimum requirement for SFTT is to have at least 3 nodes per data with no self healing possiblity(whitch require minimum 4 host with SFTT failure methode miroring).
So you can start with is 3+3+1 as mimum requirement to have failure tolerence across sites and host failure tolerence at local site.
Concerning the self healing, in case of FTM= mirroring it require minimum 4 nodes because in case of one node failure, vSAN cluster will be able resync the data and have all your components compliant with the vSAN storage policy. In this case, even with one node failure, you will have data on host1 witch is duplicated in host2 and the witness object on host3.
regarding the link let me share with you : link1 and link 2.
Please let me know it you need further assistance.
Best regards,
Hassan BEN TAHER