when `license= NULL' this function will look in your DESCRIPTION file and search for the "license:" part. If it matches GPL or MIT a custom badge will be created. If it does not match, a general badge will be created with the name of the license in grey.
badge_license(license = NULL, location = ".")License, for example GPL-3, MIT, etc. Alternatively, leaving it empty will search.
defaults to current directory
markdown
Other badges: badge_codecov,
badge_cran_ago,
badge_cran_date,
badge_cran_version_ago,
badge_cran_version_release,
badge_cran,
badge_github_fork,
badge_github_star,
badge_last_change_static,
badge_last_change,
badge_minimal_r_version,
badge_packageversion,
badge_projectstatus,
badge_rank,
badge_rdocumentation,
badge_thanks_md, badge_travis