fix: use postcss-syntax fork until 1.x (#240)

* fix: use postcss-syntax fork until 1.x

Fixes #239

postcss-syntax uses require statements without string literals, so the
bundler is unable to recognize the dependencies at bundle time. This
fork uses static requires for packages used in vscode-stylelint to allow
the proper resolution of packages. This fix, along with the fix for
#237, will no longer be required for 1.x of this package, which will be
tracking stylelint 14.

see adalinesimonian/postcss-syntax@ba1d4a6

package.json

@@ -200,6 +200,7 @@
     "fast-diff": "^1.2.0",
     "lodash": "^4.17.20",
     "path-is-inside": "^1.0.2",
+    "postcss-syntax": "https://[email protected]/adalinesimonian/postcss-syntax.git#bundler-friendly",
     "pkg-dir": "^5.0.0",
     "stylelint": "^13.13.1",
     "vscode-languageclient": "^6.2.0-next.1",