Add some useful snippets for podman and slurm

podman-snippets.md

+# Useful podman snippets
+
+## Remove all currently not required resources
+
+```bash
+podman system prune -a
+```
+
+If your need more fine grained control replace `system` with `container|image|volume|...`.

slurm-snippets.md

+# Useful slurm snippets
+
+## Open an interactive shell on a cluster node
+
+```bash
+srun --pty -c 1 --mem=4G /bin/bash
+```
+
+## Get all node names
+
+```bash
+scontrol show nodes | awk '/NodeName/ {print $1}' | cut -d= -f2
+```