feat: pull country or language by code.

* feat: pull country or language by code.

This differs from the existing `search` functionality in that it allows
you to explicitly pull back a single country or language instead of
anything that matches (which could result in more items returned than
expected).

* refactor(types): add new types for the affected endpoints.
* docs(readme): update to include examples for new functionality.
* test: expand tests to include new parameters.
* feat(package): upgrade dependencies to the latest versions.
* fix(eslint): adjust configuration based on an updated dependency.
* docs(license): bump the year of the license.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "holidayapi",
-  "version": "3.0.0",
+  "version": "3.1.0",
   "description": "Official Node.js library for Holiday API",
   "main": "dist/index.js",
   "types": "dist/index.d.ts",
@@ -24,26 +24,28 @@
     "node": ">= 8.0.0"
   },
   "devDependencies": {
-    "@types/jest": "^24.0.22",
+    "@types/jest": "^25.1.2",
     "@types/nock": "^11.1.0",
-    "@types/node": "^12.12.7",
-    "@types/node-fetch": "^2.5.3",
-    "@typescript-eslint/eslint-plugin": "^2.7.0",
-    "@typescript-eslint/parser": "^2.7.0",
-    "coveralls": "^3.0.7",
-    "eslint": "^6.6.0",
+    "@types/node": "^13.7.1",
+    "@types/node-fetch": "^2.5.4",
+    "@typescript-eslint/eslint-plugin": "^2.19.2",
+    "@typescript-eslint/parser": "^2.19.2",
+    "coveralls": "^3.0.9",
+    "eslint": "^6.8.0",
     "eslint-config-airbnb-base": "^14.0.0",
-    "eslint-plugin-import": "^2.18.2",
-    "eslint-plugin-jest": "^23.0.3",
-    "jest": "^24.9.0",
-    "nock": "^11.7.0",
-    "ts-jest": "^24.1.0",
-    "typescript": "^3.7.2"
+    "eslint-plugin-import": "^2.20.1",
+    "eslint-plugin-jest": "^23.7.0",
+    "jest": "^25.1.0",
+    "nock": "^11.8.2",
+    "ts-jest": "^25.2.0",
+    "typescript": "^3.7.5"
   },
   "dependencies": {
     "node-fetch": "^2.6.0"
   },
   "scripts": {
+    "build": "tsc",
+    "lint": "eslint --ext .js,.ts src/ tests/",
     "test": "jest --coverage --coverageReporters=text-lcov | coveralls"
   }
 }