[server] Fix uploads on self-hosted Docker when running on Windows

On our Discord @Degos ran into an issue where their uploads to the self hosted
docker compose cluster were failing. On debugging, it was found that the
line-endings in `server/scripts/compose/minio-provision.sh` were set to CRLF,
causing the script to fail when run inside Docker. The minIO buckets never got
provisioned, and so the uploads would fail with

    <Code>NoSuchBucket</Code>
    <Message>The specified bucket does not exist</Message>

To fix this, we add a new .gitattributes that enforces the LF for the scripts
that run inside Docker. To (perhaps too preemptively) guard against similar
issues in other scenarios, turn this on for all shell scripts.

Refs:
- https://stackoverflow.com/questions/29603737/bash-seamlessly-run-scripts-with-crlf-line-endings
- https://docs.github.com/en/get-started/getting-started-with-git/configuring-git-to-handle-line-endings

.gitattributes

@@ -0,0 +1,3 @@
+# Set line endings of shell scripts to LF, even on Windows, otherwise execution
+# within Docker fails.
+*.sh text eol=lf