Import the GitHub type from @actions/github with file extension syntax

This improves the code compatibility with the ESM syntax.
Issue #603

.eslintrc.json

@@ -10,6 +10,7 @@
   "rules": {
     "i18n-text/no-en": "off",
     "eslint-comments/no-use": "off",
+    "import/extensions": [ "error", "ignorePackages", { "ts": "never" } ],
     "import/no-namespace": "off",
     "import/no-named-as-default": "off",
     "no-shadow": "off",

src/input-providers/artifact-provider.ts

@@ -1,6 +1,6 @@
 import * as core from '@actions/core'
 import * as github from '@actions/github'
-import {GitHub} from '@actions/github/lib/utils'
+import type {GitHub} from '@actions/github/lib/utils.js'
 
 import Zip from 'adm-zip'
 import picomatch from 'picomatch'

src/main.ts

@@ -1,6 +1,6 @@
 import * as core from '@actions/core'
 import * as github from '@actions/github'
-import {GitHub} from '@actions/github/lib/utils'
+import type {GitHub} from '@actions/github/lib/utils.js'
 
 import {ArtifactProvider} from './input-providers/artifact-provider'
 import {LocalFileProvider} from './input-providers/local-file-provider'

src/utils/github-utils.ts

@@ -1,7 +1,7 @@
 import {createWriteStream} from 'fs'
 import * as core from '@actions/core'
 import * as github from '@actions/github'
-import {GitHub} from '@actions/github/lib/utils'
+import type {GitHub} from '@actions/github/lib/utils.js'
 import type {PullRequest} from '@octokit/webhooks-types'
 import * as stream from 'stream'
 import {promisify} from 'util'