Wfpm

* added template README.md in the package folder (66)

Bug fixes:
* perform clean up when wfpm nextver failed unexpectedly (62)
* parse out version string properly in scripts (63)
* older version of git common causes false alarm about branch not clean (65)

* Updated GitHub Actions code to include run package command as part of the package release note

* Added singularity image file name patterns to .gitignore, addressed 48
* Improved package validation, addressed 51
* Updated messages for `wfpm init` command for better clarity, addressed 55
* Added package URI in release note, addressed 56
* Fixed checker.nf in tool/workflow templates

* perform package integrity check when run `wfpm test`, addressed 37
* perform update on version of checker.nf script for `wfpm nextver`, addressed 38
* support creating a new workflow package without specifying any dependencies, addressed 33
* typo fixes to documentation contributed from aferriz, thanks :blush:

* handle git branches/tages (not managed by `wfpm`) not sortable using `LooseVersion`, fall back to normal sort
* made the example implementation of `file_smart_diff` in checker script a bit cleaner