Automatic detection of most recent released version

[amstilp]

Noting in case we need this for later. If a release is in progress, the code pulls the in-progress information, not the most recently released version.

The node for the first released version can be identified using this syntax:

study_xml %>% xml_find_first(".//Status[@name='released']") %>% xml_parent()

Do we want to add an argument or flag somewhere that lets you choose between most recently released version and current version? Or maybe something like find_most_recent_released_version to pull the most recent released version, which can then be passed to the other xml_* functions?