Bump acorn from 6.4.0 to 6.4.1

Bumps [acorn](https://github.com/acornjs/acorn) from 6.4.0 to 6.4.1.
- [Release notes](https://github.com/acornjs/acorn/releases)
- [Commits](acornjs/acorn@6.4.0...6.4.1)

Signed-off-by: dependabot[bot] <[email protected]>

yarn.lock

@@ -2701,9 +2701,9 @@ accepts@~1.3.7:
     negotiator "0.6.2"
 
 acorn@^6.2.1:
-  version "6.4.0"
-  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.4.0.tgz#b659d2ffbafa24baf5db1cdbb2c94a983ecd2784"
-  integrity sha512-gac8OEcQ2Li1dxIEWGZzsp2BitJxwkwcOm0zHAJLcPJaVvm58FRnk6RkuLRpU1EujipU2ZFODv2P9DLMfnV8mw==
+  version "6.4.1"
+  resolved "https://registry.yarnpkg.com/acorn/-/acorn-6.4.1.tgz#531e58ba3f51b9dacb9a6646ca4debf5b14ca474"
+  integrity sha512-ZVA9k326Nwrj3Cj9jlh3wGFutC2ZornPNARZwsNYqQYgN0EsV2d53w5RN/co65Ohn4sUAUtb1rSUAOD6XN9idA==
 
 agent-base@4, agent-base@^4.3.0:
   version "4.3.0"
@@ -12986,6 +12986,13 @@ yallist@^3.0.0, yallist@^3.0.2, yallist@^3.0.3:
   resolved "https://registry.yarnpkg.com/yallist/-/yallist-3.1.1.tgz#dbb7daf9bfd8bac9ab45ebf602b8cbad0d5d08fd"
   integrity sha512-a4UGQaWPH59mOXUYnAG2ewncQS4i4F43Tv3JoAM+s2VDAmS9NsK8GpDMLrCHPksFT7h3K6TOoUNn2pb7RoXx4g==
 
+[email protected]:
+  version "0.2.1"
+  resolved "https://registry.yarnpkg.com/yang-sprotty/-/yang-sprotty-0.2.1.tgz#cceea399f833c6b2ef46c6682d7d9f9097f643e5"
+  integrity sha512-rthtiq75bFTfG0JPlrFew519GDZdm94XJ5EnXjObf+270vcPt6XFB/fFxX4UBVoBdvLlcy1V9W/fRCzKpY1g5A==
+  dependencies:
+    sprotty "^0.8.0"
+
 [email protected], yargs-parser@^13.1.2:
   version "13.1.2"
   resolved "https://registry.yarnpkg.com/yargs-parser/-/yargs-parser-13.1.2.tgz#130f09702ebaeef2650d54ce6e3e5706f7a4fb38"