Add license-is-osi-or-fsf-approved rule type.

This rule type checks that the license detected by GitHub is approved
by either OSI or FSF. It uses two data sources, one to call GitHub API
to get the SPDX identifier of the license, and another one to get the
updated list of licenses approved by from SPDX repository.

This rule can be used to implement `OSPS-LE-02`.

data-sources/osi.yaml → data-sources/spdx.yaml

@@ -1,6 +1,6 @@
 version: v1
 type: data-source
-name: osi
+name: spdx
 context: {}
 rest:
   def: