* Update roxygen2 doc. Co-authored-by: fis <jm.yuan@outlook.com>
* Fix loading text data. * Fix config regex. * Try to explain the error better in exception. * Update doc.
* Reorganize contributor's doc * Address comments from @trivialfis * Address @sriramch's comment: include ABI compatibility guarantee * Address @rongou's comment * Postpone ABI compatibility guarantee for now