feat: enable Knip's treatConfigHintsAsErrors (#2300)

## PR Checklist

- [x] Addresses an existing open issue: fixes #2213
- [x] That issue was marked as [`status: accepting
prs`](https://github.com/JoshuaKGoldberg/create-typescript-app/issues?q=is%3Aopen+is%3Aissue+label%3A%22status%3A+accepting+prs%22)
- [x] Steps in
[CONTRIBUTING.md](https://github.com/JoshuaKGoldberg/create-typescript-app/blob/main/.github/CONTRIBUTING.md)
were taken

## Overview

🎁

Author: JoshuaKGoldberg

knip.json

@@ -8,5 +8,6 @@
 		"trash-cli"
 	],
 	"ignoreExportsUsedInFile": { "interface": true, "type": true },
-	"project": ["src/**/*.ts"]
+	"project": ["src/**/*.ts"],
+	"treatConfigHintsAsErrors": true
 }

src/blocks/blockKnip.test.ts

@@ -69,7 +69,7 @@ describe("blockKnip", () => {
 			    },
 			  ],
 			  "files": {
-			    "knip.json": "{"$schema":"https://unpkg.com/knip@5.71.0/schema.json","ignoreExportsUsedInFile":{"interface":true,"type":true}}",
+			    "knip.json": "{"$schema":"https://unpkg.com/knip@5.71.0/schema.json","ignoreExportsUsedInFile":{"interface":true,"type":true},"treatConfigHintsAsErrors":true}",
 			  },
 			}
 		`);
@@ -140,7 +140,7 @@ describe("blockKnip", () => {
 			    },
 			  ],
 			  "files": {
-			    "knip.json": "{"$schema":"https://unpkg.com/knip@5.71.0/schema.json","entry":["src/index.ts"],"ignoreDependencies":["abc","def"],"ignoreExportsUsedInFile":{"interface":true,"type":true},"project":["src/**/*.ts"]}",
+			    "knip.json": "{"$schema":"https://unpkg.com/knip@5.71.0/schema.json","entry":["src/index.ts"],"ignoreDependencies":["abc","def"],"ignoreExportsUsedInFile":{"interface":true,"type":true},"project":["src/**/*.ts"],"treatConfigHintsAsErrors":true}",
 			  },
 			}
 		`);
@@ -216,7 +216,7 @@ describe("blockKnip", () => {
 			    },
 			  ],
 			  "files": {
-			    "knip.json": "{"$schema":"https://unpkg.com/knip@5.71.0/schema.json","ignoreExportsUsedInFile":{"interface":true,"type":true}}",
+			    "knip.json": "{"$schema":"https://unpkg.com/knip@5.71.0/schema.json","ignoreExportsUsedInFile":{"interface":true,"type":true},"treatConfigHintsAsErrors":true}",
 			  },
 			}
 		`);

src/blocks/blockKnip.ts

@@ -82,6 +82,7 @@ export const blockKnip = base.createBlock({
 						type: true,
 					},
 					project: project?.sort(),
+					treatConfigHintsAsErrors: true,
 				}),
 			},
 		};