Fix image links.

Canonicalizing in the nix build was causing the image links to reference the nix build path. By switching to lexical normalization, the paths are being properly calculated.

flake.lock

@@ -8,11 +8,11 @@
         "rust-overlay": "rust-overlay"
       },
       "locked": {
-        "lastModified": 1784333070,
+        "lastModified": 1792617478,
-        "narHash": "sha256-3WkxaHOS13vFBtQFBmGIPScQZDNLk5bqCAY9qBJASl0=",
+        "narHash": "sha256-ctFfFI7qlZxv6s8nznps7KYp/QQ1zzbMKCgLtl7YYRA=",
         "ref": "refs/heads/main",
-        "rev": "faf279292ad20783775d909b96815f7ca2843b85",
+        "rev": "1c369e4b25caf4dd9a962340a770fbd6e543820a",
-        "revCount": 327,
+        "revCount": 331,
         "type": "git",
         "url": "https://code.fizz.buzz/talexander/natter.git"
       },