docs: add nix-dokploy to goodies

[el-kurto]

Adds nix-dokploy to the goodies page — a NixOS module that runs Dokploy using declarative systemd units.

As discussed in Dokploy/dokploy#2632

Greptile Summary

This PR adds a new entry for nix-dokploy — a NixOS module that runs Dokploy using declarative systemd units — to the community goodies documentation page. The change is a single-line addition that follows the existing format consistently.

• The new entry is well-formatted and the description is clear and informative.
• There is a pre-existing duplicate list number 5 on line 11 (Dokploy JS Sdk), which causes all subsequent items to be numbered one less than their actual position. The new entry is labelled 9 but is logically the 10th item. Fixing the duplicate 5 along with this PR would keep the list accurate.

Confidence Score: 5/5

• This PR is safe to merge — it is a simple, isolated documentation addition with no code changes.
• The change is a single line added to a Markdown documentation file. The formatting is consistent with existing entries and the linked repository is valid. The only minor issue (off-by-one list numbering) is a pre-existing problem not introduced by this PR.
• No files require special attention.

_{Last reviewed commit: "docs: add nix-dokplo..."}

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