Add Babel plugin for nullish coalescing operator

Author: grubersjoe

babel.config.json

@@ -1,3 +1,4 @@
 {
-  "presets": ["@babel/preset-env", "@babel/preset-typescript", "@babel/preset-react"]
+  "presets": ["@babel/preset-env", "@babel/preset-typescript", "@babel/preset-react"],
+  "plugins": ["@babel/plugin-proposal-nullish-coalescing-operator"]
 }

package.json

@@ -1,6 +1,6 @@
 {
   "name": "react-github-calendar",
-  "version": "3.0.4",
+  "version": "3.0.5",
   "description": " A flexible React component to display a GitHub contributions graph",
   "author": "Jonathan Gruber <[email protected]>",
   "license": "MIT",
@@ -19,22 +19,22 @@
     "start": "rollup -c -w"
   },
   "dependencies": {
+    "@babel/plugin-proposal-nullish-coalescing-operator": "^7.14.5",
     "date-fns": "^2.23.0",
     "react-activity-calendar": "^1.3.3",
     "tinycolor2": "^1.4.0"
   },
   "devDependencies": {
-    "@babel/core": "^7.14.8",
-    "@babel/preset-env": "^7.14.8",
+    "@babel/core": "^7.15.0",
+    "@babel/preset-env": "^7.15.0",
     "@babel/preset-react": "^7.10.1",
-    "@babel/preset-typescript": "^7.10.1",
-    "@types/jest": "^26.0.24",
-    "@types/react": "^17.0.15",
+    "@babel/preset-typescript": "^7.15.0",
+    "@types/react": "^17.0.19",
     "@types/react-dom": "^17.0.9",
     "@types/react-tooltip": "^4.2.4",
     "@types/tinycolor2": "^1.4.3",
-    "@typescript-eslint/eslint-plugin": "^4.28.5",
-    "@typescript-eslint/parser": "^4.28.5",
+    "@typescript-eslint/eslint-plugin": "^4.29.3",
+    "@typescript-eslint/parser": "^4.29.3",
     "babel-eslint": "^10.1.0",
     "cross-env": "^7.0.2",
     "eslint": "^7.32.0",
@@ -45,14 +45,14 @@
     "react": "^17.0.2",
     "react-dom": "^17.0.2",
     "react-scripts": "^4.0.3",
-    "rollup": "^2.55.1",
+    "rollup": "^2.56.3",
     "rollup-plugin-babel": "^4.4.0",
     "rollup-plugin-commonjs": "^10.1.0",
     "rollup-plugin-copy": "^3.3.0",
     "rollup-plugin-filesize": "^9.0.1",
     "rollup-plugin-node-resolve": "^5.2.0",
     "rollup-plugin-peer-deps-external": "^2.2.2",
-    "rollup-plugin-postcss": "^4.0.0",
+    "rollup-plugin-postcss": "^4.0.1",
     "rollup-plugin-url": "^3.0.1",
     "typescript": "^4.3.5"
   },