Add Postgres 13 to latest versions

[cayetanobv]

Describe the solution you'd like
Postgres 13 was released on September 24:
https://www.postgresql.org/about/news/postgresql-13-released-2077/

We can add it to pgRouting last release (+ master and development versions).

[dkastl]

I also want to to add it to CI ... probably by the end of the week: pgRouting/pgrouting#1612

[cayetanobv]

Solved with PR #37

[cayetanobv]

Building images now:
https://hub.docker.com/repository/docker/pgrouting/pgrouting/builds

@dkastl I will send an email to pgrouting list announcing new pg13.

[dkastl]

Thank you!