Add default license for bids-standard repositories

[tsalo]

This stems from bids-standard/bids-specification#892 (comment). It just might be good to have a recommended license for software housed under the bids-standard organization.

[bendhouseart]

Issue #7 may close this.

[christinerogers]

status: too low priority. bumping to backlog.

[Remi-Gau]

would remove from the GSOD project