[ssr] Improve module loader and add a module cache that track imports. (lit#2288)

Author: justinfagnani

.changeset/spicy-dolphins-wait.md

@@ -0,0 +1,5 @@
+---
+'@lit-labs/ssr': major
+---
+
+Refactor the import-module into a class-based ModuleLoader API. Adds a module cache that tracks dependencies between modules.

.eslintignore

@@ -149,9 +149,13 @@ packages/labs/scoped-registry-mixin/scoped-registry-mixin.*
 packages/labs/ssr/demo/
 packages/labs/ssr/lib/
 packages/labs/ssr/node_modules/
-packages/labs/ssr/test/
+packages/labs/ssr/test/**/*.js
+packages/labs/ssr/test/**/*.js.map
+packages/labs/ssr/test/**/*.d.ts
+packages/labs/ssr/test/**/*.d.ts.map
 packages/labs/ssr/index.*
 !packages/labs/ssr/custom_typings/*.d.ts
+
 packages/labs/ssr-client/development/
 packages/labs/ssr-client/directives/
 packages/labs/ssr-client/controllers/

.prettierignore

@@ -135,9 +135,13 @@ packages/labs/scoped-registry-mixin/scoped-registry-mixin.*
 packages/labs/ssr/demo/
 packages/labs/ssr/lib/
 packages/labs/ssr/node_modules/
-packages/labs/ssr/test/
+packages/labs/ssr/test/**/*.js
+packages/labs/ssr/test/**/*.js.map
+packages/labs/ssr/test/**/*.d.ts
+packages/labs/ssr/test/**/*.d.ts.map
 packages/labs/ssr/index.*
 !packages/labs/ssr/custom_typings/*.d.ts
+
 packages/labs/ssr-client/development/
 packages/labs/ssr-client/directives/
 packages/labs/ssr-client/controllers/

packages/labs/ssr/.gitignore

@@ -1,6 +1,9 @@
 /demo/
 /lib/
 /node_modules/
-/test/
+/test/**/*.js
+/test/**/*.js.map
+/test/**/*.d.ts
+/test/**/*.d.ts.map
 /index.*
-!/custom_typings/*.d.ts
+!/custom_typings/*.d.ts