Update mkdirp in group main to the latest version � (#757)

Summary:
## The dependency [mkdirp](https://github.com/isaacs/node-mkdirp) was updated from `0.5.1` to `1.0.0`.
This version is **not covered** by your **current version range**.

If you don’t accept this pull request, your project will work just like it did before. However, you might be missing out on a bunch of new features, fixes and/or performance improvements from the dependency update.

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**Publisher:** [isaacs](https://www.npmjs.com/~isaacs)
**License:** MIT

[Find out more about this release](https://github.com/isaacs/node-mkdirp).

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<details>
  <summary>FAQ and help</summary>

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Your [Greenkeeper](https://greenkeeper.io) bot 🌴
Pull Request resolved: https://github.com/facebook/flipper/pull/757

Reviewed By: mweststrate

Differential Revision: D19578531

Pulled By: passy

fbshipit-source-id: b31ca29fabf263978242af464882cc530ff6564d

package.json

@@ -149,7 +149,7 @@
     "live-plugin-manager": "^0.14.0",
     "lodash.debounce": "^4.0.8",
     "lodash.isequal": "^4.5.0",
-    "mkdirp": "^0.5.1",
+    "mkdirp": "^1.0.0",
     "node-fetch": "^2.3.0",
     "npm-api": "^1.0.0",
     "open": "^7.0.0",

yarn.lock

@@ -6349,6 +6349,11 @@ mkdirp@0.5.1, mkdirp@0.x, mkdirp@^0.5.0, mkdirp@^0.5.1:
   dependencies:
     minimist "0.0.8"
 
+mkdirp@^1.0.0:
+  version "1.0.2"
+  resolved "https://registry.yarnpkg.com/mkdirp/-/mkdirp-1.0.2.tgz#5ccd93437619ca7050b538573fc918327eba98fb"
+  integrity sha512-N2REVrJ/X/jGPfit2d7zea2J1pf7EAR5chIUcfHffAZ7gmlam5U65sAm76+o4ntQbSRdTjYf7qZz3chuHlwXEA==
+
 moment@^2.15.1, moment@^2.24.0:
   version "2.24.0"
   resolved "https://registry.yarnpkg.com/moment/-/moment-2.24.0.tgz#0d055d53f5052aa653c9f6eb68bb5d12bf5c2b5b"