Update is-plain-obj requirement from ^1.1.0 to ^2.0.0 (#11)

Updates the requirements on [is-plain-obj](https://github.com/sindresorhus/is-plain-obj) to permit the latest version.
- [Release notes](https://github.com/sindresorhus/is-plain-obj/releases)
- [Commits](sindresorhus/is-plain-obj@v1.1.0...v2.0.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

package.json

@@ -34,7 +34,7 @@
     "eslint-config-tc": "^5.1.0",
     "eslint-formatter-pretty": "^2.1.1",
     "eslint-plugin-import": "^2.15.0",
-    "is-plain-obj": "^1.1.0",
+    "is-plain-obj": "^2.0.0",
     "mocha": "^6.1.4",
     "npm-package-json-lint": "^3.4.1",
     "temp-write": "^4.0.0"