Externalize spec typings, use eslint.

Tslint is deprecated, as such we have moved to eslint. Linted the project with more
stringent rules. The configuration will be changed as we figure out which rules we
should keep.

.eslintignore

@@ -0,0 +1,2 @@
+node_modules
+dist

.eslintrc.json

@@ -0,0 +1,42 @@
+{
+    "root": true,
+    "parser": "@typescript-eslint/parser",
+    "plugins": [
+        "@typescript-eslint"
+    ],
+    "extends": [
+        "eslint:recommended",
+        "plugin:@typescript-eslint/eslint-recommended",
+        "plugin:@typescript-eslint/recommended"
+    ],
+    "rules": {
+        "semi": "off",
+        "@typescript-eslint/semi": [
+            "error",
+            "never"
+        ],
+        "quotes": "off",
+        "@typescript-eslint/quotes": [
+            "error",
+            "single"
+        ],
+        "indent": "off",
+        "@typescript-eslint/indent": [
+            "error",
+            4
+        ],
+        "@typescript-eslint/member-delimiter-style": [
+            "error",
+            {
+                "multiline": {
+                    "delimiter": "none",
+                    "requireLast": false
+                },
+                "singleline": {
+                    "delimiter": "comma",
+                    "requireLast": false
+                }
+            }
+        ]
+    }
+}