ci: rename configs to .bash

Avoids locale linting error and indicates that the config files must use bash, not some other variant of shell script.

Author: Sjors

ci/README.md

@@ -16,9 +16,9 @@ All CI is just bash and nix.
 To run jobs locally:
 
 ```bash
-CI_CONFIG=ci/configs/default.sh ci/scripts/run.sh
-CI_CONFIG=ci/configs/llvm.sh    ci/scripts/run.sh
-CI_CONFIG=ci/configs/gnu32.sh   ci/scripts/run.sh
+CI_CONFIG=ci/configs/default.bash ci/scripts/run.sh
+CI_CONFIG=ci/configs/llvm.bash    ci/scripts/run.sh
+CI_CONFIG=ci/configs/gnu32.bash   ci/scripts/run.sh
 ```
 
 By default CI jobs will reuse their build directories. `CI_CLEAN=1` can be specified to delete them before running instead.