document useful queries

[mr-c]

1. select license_link, count(*) from workflow group by license_link order by 2 desc;

                                license_link                                 | count 
-----------------------------------------------------------------------------+-------
 https://spdx.org/licenses/Apache-2.0                                        |    47
 https://spdx.org/licenses/MIT                                               |    24
                                                                             |    24
 https://spdx.org/licenses/GPL-3.0                                           |     3
 https://raw.githubusercontent.com/ncbi/cwl-ngs-workflows-cbb/master/LICENSE |     2
 https://spdx.org/licenses/BSD-2-Clause                                      |     2
 https://spdx.org/licenses/BSD-3-Clause                                      |     1
 https://spdx.org/licenses/Unlicense                                         |     1
 https://raw.githubusercontent.com/yyoshiaki/VIRTUS/master/LICENCE.md        |     1