Update dependency @mkobayashime/shared-config to v3

This PR contains the following updates:

| Package | Change |
|---|---|
| @mkobayashime/shared-config | 2.0.0 → 3.0.0 |

Also adds eslint-config-flat-gitignore required for shared-config v3.

Author: renovate[bot]

bun.lock

@@ -9,12 +9,13 @@
 	"type": "module",
 	"devDependencies": {
 		"@biomejs/biome": "2.3.11",
-		"@mkobayashime/shared-config": "2.0.0",
+		"@mkobayashime/shared-config": "3.0.0",
 		"@types/glob": "9.0.0",
 		"@types/node": "25.0.10",
 		"bookmarklets-cli": "1.1.5",
 		"comment-parser": "1.4.4",
 		"eslint": "9.39.2",
+		"eslint-config-flat-gitignore": "2.1.0",
 		"fp-ts": "2.16.11",
 		"glob": "11.0.3",
 		"typescript": "5.9.3",