CSS extraction and code-splitting

closes #388

src/core/create_compilers/interfaces.ts

@@ -0,0 +1,39 @@
+import { ManifestData, Dirs } from '../../interfaces';
+
+export type Chunk = {
+	file: string;
+	imports: string[];
+	modules: string[];
+}
+
+export type CssFile = {
+	id: string;
+	code: string;
+};
+
+export class CompileError {
+	file: string;
+	message: string;
+}
+
+export interface CompileResult {
+	duration: number;
+	errors: CompileError[];
+	warnings: CompileError[];
+	chunks: Chunk[];
+	assets: Record<string, string>;
+	css_files: CssFile[];
+
+	to_json: (manifest_data: ManifestData, dirs: Dirs) => BuildInfo
+}
+
+export type BuildInfo = {
+	bundler: string;
+	shimport: string;
+	assets: Record<string, string>;
+	legacy_assets?: Record<string, string>;
+	css: {
+		main: string | null,
+		chunks: Record<string, string[]>
+	}
+}