fix: remove the tns-core-modules dependency in order to allow @nativescrip/core migration

The parse method content is the same:
Old:
https://github.com/NativeScript/NativeScript/blob/fc2a233e9598def50969247c1516c32260b7e283/nativescript-core/css/lib/parse/index.js
New:
https://github.com/reworkcss/css/blob/v2.2.1/lib/parse/index.js

Author: DimitarTachev

Diff for: css2json-loader.ts

@@ -1,11 +1,7 @@
-import { parse, Rule, SyntaxTree } from "tns-core-modules/css";
+import { parse, Import, Stylesheet } from "css";
 import { loader } from "webpack";
 import { getOptions } from "loader-utils";
 
-interface ImportRule extends Rule {
-    import: string;
-}
-
 const betweenQuotesPattern = /('|")(.*?)\1/;
 const unpackUrlPattern = /url\(([^\)]+)\)/;
 const inlineLoader = "!nativescript-dev-webpack/css2json-loader?useForImports!"
@@ -33,18 +29,18 @@ const loader: loader.Loader = function (content: string, map) {
     this.callback(null, `${dependencies.join("\n")}module.exports = ${str};`, map);
 }
 
-function getImportRules(ast: SyntaxTree): ImportRule[] {
+function getImportRules(ast: Stylesheet): Import[] {
     if (!ast || (<any>ast).type !== "stylesheet" || !ast.stylesheet) {
         return [];
     }
-    return <ImportRule[]>ast.stylesheet.rules
+    return <Import[]>ast.stylesheet.rules
         .filter(rule => rule.type === "import" && (<any>rule).import)
 }
 
 /**
  * Extracts the url from import rule (ex. `url("./platform.css")`)
  */
-function extractUrlFromRule(importRule: ImportRule): string {
+function extractUrlFromRule(importRule: Import): string {
     const urlValue = importRule.import;
 
     const unpackedUrlMatch = urlValue.match(unpackUrlPattern);

Diff for: package.json

@@ -50,6 +50,7 @@
     "@angular-devkit/core": "8.2.0",
     "clean-webpack-plugin": "~1.0.0",
     "copy-webpack-plugin": "~4.6.0",
+    "css": "2.2.1",
     "css-loader": "~2.1.1",
     "escape-string-regexp": "1.0.5",
     "fork-ts-checker-webpack-plugin": "2.0.0",
@@ -82,6 +83,7 @@
     "@angular/compiler-cli": "8.2.0",
     "@istanbuljs/nyc-config-typescript": "^0.1.3",
     "@ngtools/webpack": "8.2.0",
+    "@types/css": "0.0.31",
     "@types/jasmine": "^3.3.7",
     "@types/loader-utils": "^1.1.3",
     "@types/node": "^10.12.12",