chore(cross-env): upgrade cross-env to v 7.x

Major change includes environment deprecations, which drops support for Node < 10.x

package.json

@@ -29,7 +29,7 @@
     "chalk": "^4.1.0",
     "conditional-specs": "^1.0.1",
     "conventional-changelog": "^3.1.12",
-    "cross-env": "^5.0.0",
+    "cross-env": "^7.0.2",
     "eslint": "^4.18.1",
     "eslint-plugin-flowtype": "^2.46.1",
     "eslint-plugin-markdown": "^1.0.0-beta.6",

yarn.lock

@@ -4721,12 +4721,12 @@ create-hmac@^1.1.0, create-hmac@^1.1.2, create-hmac@^1.1.4:
     safe-buffer "^5.0.1"
     sha.js "^2.4.8"
 
-cross-env@^5.0.0:
-  version "5.1.3"
-  resolved "https://registry.yarnpkg.com/cross-env/-/cross-env-5.1.3.tgz#f8ae18faac87692b0a8b4d2f7000d4ec3a85dfd7"
+cross-env@^7.0.2:
+  version "7.0.2"
+  resolved "https://registry.yarnpkg.com/cross-env/-/cross-env-7.0.2.tgz#bd5ed31339a93a3418ac4f3ca9ca3403082ae5f9"
+  integrity sha512-KZP/bMEOJEDCkDQAyRhu3RL2ZO/SUVrxQVI0G3YEQ+OLbRA3c6zgixe8Mq8a/z7+HKlNEjo8oiLUs8iRijY2Rw==
   dependencies:
-    cross-spawn "^5.1.0"
-    is-windows "^1.0.0"
+    cross-spawn "^7.0.1"
 
 cross-spawn@^5.1.0:
   version "5.1.0"
@@ -4755,6 +4755,15 @@ cross-spawn@^7.0.0:
     shebang-command "^2.0.0"
     which "^2.0.1"
 
+cross-spawn@^7.0.1:
+  version "7.0.3"
+  resolved "https://registry.yarnpkg.com/cross-spawn/-/cross-spawn-7.0.3.tgz#f73a85b9d5d41d045551c177e2882d4ac85728a6"
+  integrity sha512-iRDPJKUPVEND7dHPO8rkbOnPpyDygcDFtWjpeWNCgy8WP2rXcxXL8TskReQl6OrB2G7+UJrags1q15Fudc7G6w==
+  dependencies:
+    path-key "^3.1.0"
+    shebang-command "^2.0.0"
+    which "^2.0.1"
+
 crypto-browserify@^3.11.0:
   version "3.12.0"
   resolved "https://registry.yarnpkg.com/crypto-browserify/-/crypto-browserify-3.12.0.tgz#396cf9f3137f03e4b8e532c58f698254e00f80ec"