chore: add config

Author: TomokiMiyauci

_test_import_map.json

@@ -0,0 +1,6 @@
+{
+  "imports": {
+    "https://deno.land/x/get_event_listeners/": "./",
+    "https://deno.land/std/": "https://deno.land/[email protected]/"
+  }
+}

deno.json

@@ -0,0 +1,20 @@
+{
+  "tasks": {
+    "test": "deno test --import-map=_test_import_map.json --doc",
+    "build:npm": "deno run -A --no-lock _tools/build_npm.ts"
+  },
+  "fmt": {
+    "exclude": ["CHANGELOG.md"]
+  },
+  "lint": {
+    "exclude": ["CHANGELOG.md"]
+  },
+  "test": {
+    "exclude": ["CHANGELOG.md", "npm"]
+  },
+  "compilerOptions": {
+    "noImplicitReturns": true,
+    "noImplicitOverride": true,
+    "noUncheckedIndexedAccess": true
+  }
+}