.eslintrc.json: enforce limit on empty lines in json5

Only allow one blank line in json5 files as well as a max of one
line at the end of the file.

See: https://eslint.org/docs/latest/rules/no-multiple-empty-lines

Author: alanorth

.eslintrc.json

@@ -246,6 +246,12 @@
           }
         ],
         "no-trailing-spaces": "error",
+        "no-multiple-empty-lines": ["error",
+          {
+            "max": 1,
+            "maxEOF": 1
+          }
+        ],
         "jsonc/comma-dangle": [
           "error",
           "always-multiline"