Rename boundaries_osm_query.txt to boundaries_osm_query.overpassql #1
Description
*.overpassql is now the recommended file extension for Overpass QL: OSM Wiki: Overpass QL § File extension
(Disclaimer: I added that section after some discussion.)
I propose to rename all Overpass QL files in this repo to *.overpassql for consistency.
Context: GitHub's syntax highlighting engine requires that 200 repositories use the same file extension before they consider supporting that syntax and file extension: github-linguist/linguist#5890