fix: check for syntactic errors when running typescript compilation in ts projects

Currently `ts-loader` is started in `transpileOnly` mode and  webpack plugin (`ForkTsCheckerWebpackPlugin`) runs TypeScript type checker on a separate process in order to report for compilation errors. By default the plugin only checks for semantic errors and adds them to `compilation.errors`. On the other side, `WatchStateLoggerPlugin` relies on `compilation.errors` array, process them on `afterEmit` hook and reports them to NativeScript CLI.
However, `ts-loader` used in `transpileOnly` mode still reports syntactic errors but adds them to `compilation.warnings`. This is a problem, as `WatchStateLoggerPlugin` doesn't process `compilation.warnings` and this way the errors are not reported to the CLI.
Setting `checkSyntacticErrors: true` will ensure that `ForkTsCheckerWebpackPlugin` checks for both syntactic and semantic errors. This way both syntactic and semantic errors will be added to `compilation.errors` array and reported to the CLI.

Author: Fatme

templates/webpack.typescript.js

@@ -253,6 +253,7 @@ module.exports = env => {
                 tsconfig: tsConfigPath,
                 async: false,
                 useTypescriptIncrementalApi: true,
+                checkSyntacticErrors: true,
                 memoryLimit: 4096
             })
         ],