Issue awesome-selfhosted#1270: fix BSD licenses declaring a LICENSE i…

…n their GitHub repo.

This commit updates the license identifier for BSD-style licensed
projects that declare their specific license with a LICENSE file on
GitHub. Additionally, the list of licenses is updated to remove the
non-existent `BSD` short identifier and replaces it with the two
SPDX-conformant license short-identifiers, `BSD-2-Clause` and
`BSD-3-Clause` defined by SPDX and recognized by GitHub.