Update research page

[meltemozcan]

@Nellie021231 Please incorporate the following update to the research page (new parts italicized):

• Measurement invariance with categorical data (Winnie Tse; Meltem Ozcan)

After the bullet starting with "Two stage path ... " and before the bullet starting with "Developing...":

• Development of a robust and efficient to data harmonization framework for data harmonization that simultaneously links incompatible measures and adjusts for noninvariance across demographic subgroups (Mark Lai, Meltem Ozcan, & Winnie Tse, funded by the National Science Foundation)

[marklhc]

Would you like to describe your interaction research, @Gengrui-Zhang ?

[YichiZhang2024]

Please add the following update to the research page under the current projects of Multilevel Modeling @Nellie021231 :

• The impact of heteroscedasticity on standard error estimation for small, unbalanced, clustered data (Yichi Zhang & Mark Lai)