snakemake/remote_files: Add minimum version check for Snakemake

Add `min_version` in the shared `remote_files.smk` so that individual workflows 
that import it don't have to remember to add the version check. 

Based on feedback from @victorlin in mpox
<nextstrain/mpox#339 (comment)>

Author: joverlee521

snakemake/remote_files.smk

@@ -9,6 +9,10 @@ to check these ourselves to improve UX here.
 """
 
 from urllib.parse import urlparse
+from snakemake.utils import min_version
+
+# Minimum Snakemake version needed for the storage plugins
+min_version("8.0.0")
 
 # Keep a list of known public buckets, which we'll allow uncredentialled (unsigned) access to
 # We could make this config-definable in the future