use-label, ESLInt, and improved logging (#18)

Important changes: 
- Node v12 => v16, new usage of `import`/`export`
- Uses new versions of `@actions` toolkit
- Uses ESLint and fixes all lints
- Changed label configuration from `label-x` properties to `use-label`
- Replaced all instances of `console.log` with `core.debug`/`.info`/`.warning`/`.setFailed`

.eslintrc.json

@@ -0,0 +1,29 @@
+{
+    "env": {
+        "browser": true,
+        "es2021": true
+    },
+    "extends": "eslint:recommended",
+    "parserOptions": {
+        "ecmaVersion": "latest",
+        "sourceType": "module"
+    },
+    "rules": {
+        "indent": [
+            "error",
+            "tab"
+        ],
+        "linebreak-style": [
+            "error",
+            "windows"
+        ],
+        "quotes": [
+            "error",
+            "double"
+        ],
+        "semi": [
+            "error",
+            "always"
+        ]
+    }
+}

action.yml

@@ -5,21 +5,13 @@ inputs:
     description: "The GitHub token to use. Make sure to use a Personal Access Token, so PRs can be updated." 
     required: false
     default: ${{ github.token }}
-  label-name:
-    description: "The name of the label that will be added to blocked issues and pull requests."
+  use-label: 
+    description: "The name of the label to apply to blocked issues or pull requests. If not found, the default value will be used."
     required: false
     default: "blocked"
-  label-description: 
-    description: "The description of the label added to blocked issues and pull requests."
-    required: false
-    default: "This PR is waiting for one or more issues to be closed."
-  label-color: 
-    description: "The color of the label added to blocked issues and pull requests."
-    required: false
-    default: "000000"
 branding: 
   icon: "git-pull-request"
   color: "red"
 runs:
-  using: 'node12'
+  using: 'node16'
   main: 'src/index.js'