Add Custom Properties as Repository-Derived Tables

[Recurzion]

This PR adds the ability to query repository custom properties (returned as jsonb) for any repository-derived columns via sharedRepositoryColumns() and updates docs with example queries (these can be removed if not needed).

This applies to the following tables:

• github_repository
• github_my_repository
• github_team_repository
• github_search_repository
• and any other table using sharedRepositoryColumns()

Example query results

Results

select name,custom_properties  from github_my_repository where name = 'myrepo'

+----------+-------------------------------+
| name | custom_properties                 |
+----------+-------------------------------+
|myrepo |  {"key1":"value1","key2":"value2"}
+----------+-------------------------------+

select name,custom_properties -> 'myproperty' as myproperty from github_repository where  full_name = 'myorg/myrepo'

+----------+-------+
| name | myproperty|
+----------+-------+
|myrepo | "myvalue"|
+----------+-------+