fix: fix module import of local css files

There is an issue when importing local css file as module as the `css2json-loader` handles it as a module instead of a local file. So, the webpack throws an error that it is not able to find the module. This PR fixes this issue as changing the method used to get the correct file uri with the method used by `css-loader` itself - https://github.com/webpack-contrib/css-loader/blob/967fb66da2545f04055eb0900a69f86e484dd842/src/utils.js#L220.

Rel to: #1098

css2json-loader.spec.ts

@@ -38,7 +38,7 @@ describe("css2jsonLoader", () => {
 
             const loaderContext = {
                 callback: (error, source: string, map) => {
-                    expect(source).toContain(`global.registerModule("custom.css", () => require("custom.css"))`);
+                    expect(source).toContain(`global.registerModule("./custom.css", () => require("./custom.css"))`);
                     expect(source).toContain(`{"type":"declaration","property":"background-color","value":"#7f9"}`);
 
                     done();
@@ -52,7 +52,7 @@ describe("css2jsonLoader", () => {
     it("inlines css2json loader in imports if option is provided", (done) => {
         const loaderContext = {
             callback: (error, source: string, map) => {
-                expect(source).toContain(`global.registerModule("custom.css", () => require("!nativescript-dev-webpack/css2json-loader?useForImports!custom.css"))`);
+                expect(source).toContain(`global.registerModule("./custom.css", () => require("!nativescript-dev-webpack/css2json-loader?useForImports!./custom.css"))`);
                 expect(source).toContain(`{"type":"declaration","property":"background-color","value":"#7f9"}`);
 
                 done();

css2json-loader.ts

@@ -1,6 +1,6 @@
 import { parse, Import, Stylesheet } from "css";
 import { loader } from "webpack";
-import { getOptions } from "loader-utils";
+import { getOptions, urlToRequest } from "loader-utils";
 
 const betweenQuotesPattern = /('|")(.*?)\1/;
 const unpackUrlPattern = /url\(([^\)]+)\)/;
@@ -53,7 +53,7 @@ function extractUrlFromRule(importRule: Import): string {
 function createRequireUri(uri): { uri: string, requireURI: string } {
     return {
         uri: uri,
-        requireURI: uri[0] === "~" && uri[1] !== "/" ? uri.substr(1) : uri
+        requireURI: urlToRequest(uri)
     };
 }