fix(docs): mark config mount as read-only

[zygm0nt]

This default config results in the following error:

Error response from daemon: failed to create task for container: failed to create shim task: OCI runtime create failed: runc create failed: unable to start container process: error during container init: error mounting "/home/x/blocky/config.yml" to rootfs at "/app/config.yml": mount /home/x/blocky/config.yml:/app/config.yml (via /proc/self/fd/6), flags: 0x5000: not a directory: unknown: Are you trying to mount a directory onto a file (or vice-versa)? Check if the specified host path exists and is the expected type

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 94.19%. Comparing base (fe84ab8) to head (bf8de0f). Report is 144 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1624 +/- ## ========================================== + Coverage 93.88% 94.19% +0.31% ========================================== Files 78 80 +2 Lines 6361 5050 -1311 ========================================== - Hits 5972 4757 -1215 + Misses 300 210 -90 + Partials 89 83 -6 ```

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