Add Equivalence Testing

[kylehamilton]

Currently equivalence testing is only found in the SMD analysis but no where else. This makes use of TOSTER and will need some small changes to get it to work well with things like correlations.

[Trebicky]

This would be a great feature. I was currently struggling with such a need for TOSTER. I needed to compare two meta-analytic results (based on correlations), one from published and one from unpublished works. I wanted to see the difference in mean effect sizes and overlap of associated CIs and PIs. This would solve my issue.

Can we expect this feature to be implemented across MAJOR soon?