Create .gitattributes with merge strategy for po files

gitattributes (shell)

implement a special merge strategy for po files (unify headers) → this file will propagate to all git clones and prevent merge conflicts upon po header modifications in two places at once. We’ve seen this happen too often, and we want to automate this so it does not happen.

To be done: define a bit more clearly what/how to unify the po headers.

Feature Branch: https://0xacab.org/Hefee/merge-po

Parent Task: #15079 (closed)

Related issues

• Related to #15403 (closed)

Original created by @u on 15364 (Redmine)