Issue28 release to cran

[nateschor]

In #28 we prepared the package for initial submission to CRAN. The tasks we completed as well as potential follow-up issues are in the opening comment.

@jmshapir two things to draw your attention to during review are:

• changing the license in https://github.com/JMSLab/eventstudyr/commit/c09bda3a269b8df75f106fe7664962ac041b60b8
• keeping PrepareLeads() and PrepareLags() as internal functions, see https://github.com/JMSLab/eventstudyr/issues/28#issuecomment-1490532121

@SimonFreyaldenhoven @ew487 @rcalvo12 fyi

[jmshapir]

@santiagohermo @nateschor are the only open threads here those that relate to https://github.com/ryanedmundkessler/suptCriticalValue/issues/2? If so maybe @santiagohermo can approve the pull for bookkeeping purposes?

[nateschor]

@jmshapir according to this repo people have been rejected from CRAN for:

• not having their function's title in title case
• having an acronym without expanding what it means the first time it is used

I addressed both of these in https://github.com/JMSLab/eventstudyr/pull/32/commits/739f0bef59b7ee3349fc660dad8c77db20603db3.

Can you confirm that you're okay with these changes? I'll wrap up this PR afterwards! My plan is then to:

1. submit to CRAN
2. make a GitHub release incrementing the version number after we are accepted to CRAN (the R Package book suggests this order of operations since we might not be accepted to CRAN on the first try, see the numbered list at the bottom of the section here and here)

fyi @santiagohermo

[nateschor]

Summary here