Migrate from travis-ci to github actions

[ablack3]

• Add .github folder with instructions for github actions
• remove travis-ci related files
• Update website to reference github actions instead of travis-ci

Note: Website has not been rebuilt with updated Rmd files.

[ablack3]

@schuemie
Should I re-generate all the website/html files and commit them? Also there is an error when building this package on Ubuntu 20.04 (devel) that I'm not sure how to fix. https://github.com/ablack3/Hades/actions

[schuemie]

Yes, please regenerate the website. Maybe one day we can configure a GitHub Action to automatically regenerate it when the RMarkdown has changes?

This seems to be the root cause of the error on Ubuntu:

* installing *source* package ‘curl’ ...
** package ‘curl’ successfully unpacked and MD5 sums checked
** using staged installation
Package libcurl was not found in the pkg-config search path.
Perhaps you should add the directory containing `libcurl.pc'
to the PKG_CONFIG_PATH environment variable
No package 'libcurl' found
Package libcurl was not found in the pkg-config search path.
Perhaps you should add the directory containing `libcurl.pc'
to the PKG_CONFIG_PATH environment variable
No package 'libcurl' found
Using PKG_CFLAGS=
Using PKG_LIBS=-lcurl
------------------------- ANTICONF ERROR ---------------------------
ERROR: configuration failed for package ‘curl’
Configuration failed because libcurl was not found. Try installing:
* removing ‘/home/runner/work/_temp/Library/curl’
 * deb: libcurl4-openssl-dev (Debian, Ubuntu, etc)
 * rpm: libcurl-devel (Fedora, CentOS, RHEL)
 * csw: libcurl_dev (Solaris)
If libcurl is already installed, check that 'pkg-config' is in your
PATH and PKG_CONFIG_PATH contains a libcurl.pc file. If pkg-config
is unavailable you can set INCLUDE_DIR and LIB_DIR manually via:
R CMD INSTALL --configure-vars='INCLUDE_DIR=... LIB_DIR=...'

Any thoughts on how to install the libcurl library before running the test script?