CCV and TSCB standard errors

[nilshg]

These are the new types of standard errors introduced by Abadie et al. in https://economics.mit.edu/sites/default/files/2022-09/When%20Should%20You%20Adjust%20Standard%20Errors%20for%20Clustering.pdf

[nilshg]

Code from the published paper is here: https://dataverse.harvard.edu/dataset.xhtml?persistentId=doi:10.7910/DVN/27VMOT