pgsql: Add Dockerfile for github.com/anthropics/oss-scanner.

Add Dockerfile for github.com/anthropics/oss-scanner.

This has no effect on normal use of this repository. The scanner clones
this repository and locates this file. While we could store it in the
scanner configuration, storing it here simplifies keeping CI and this in
sync. References to postgresql/project.yaml are forward-looking; see
github.com/nmisch/oss-scanner/blob/enroll-postgresql/projects/postgresql/project.yaml
for the planned future content. Claude wrote some of this.

Reviewed-by: Sehrope Sarkuni <sehrope(at)jackdb(dot)com>
Reviewed-by: Ayush Tiwari <ayushtiwari(dot)slg01(at)gmail(dot)com>
Reviewed-by: Andres Freund <andres(at)anarazel(dot)de>
Discussion: https://postgr.es/m/20261017032215.26.noahmisch@microsoft.com

Branch
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master

Details
-------
https://git.postgresql.org/pg/commitdiff/ddd468cacf0d5d6f124c39439505ab93d31ac65b

Modified Files
--------------
src/tools/oss-scanner/Dockerfile | 77 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 77 insertions(+)