Switch from ts-node to tsc-watch for faster watch restarts; move format npm script to project root

backend/register-tsconfig-paths.js

@@ -0,0 +1,18 @@
+/**
+ * See:
+ * https://github.com/dividab/tsconfig-paths
+ * https://github.com/TypeStrong/ts-node/issues/138
+ * https://github.com/TypeStrong/ts-node/issues/138#issuecomment-519602402
+ * https://github.com/TypeStrong/ts-node/pull/254
+ */
+
+const path = require('path');
+const tsconfig = require('./tsconfig.json');
+const tsconfigPaths = require('tsconfig-paths');
+
+// E.g. ./dist/backend
+const baseUrl = path.resolve(tsconfig.compilerOptions.outDir, path.basename(__dirname));
+tsconfigPaths.register({
+  baseUrl,
+  paths: tsconfig.compilerOptions.paths || [],
+});