refactor(starter): upgrade to new version of gatsby

internal/gatsby/constants/index.ts

@@ -0,0 +1,2 @@
+export { default as routes } from "./routes";
+export { default as templates } from "./templates";

internal/gatsby/constants/routes.ts

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+const routes = Object.freeze({
+  notFoundRoute: "/404",
+  categoriesListRoute: "/categories",
+  categoryRoute: "/category",
+  tagsListRoute: "/tags",
+  tagRoute: "/tag",
+  indexRoute: "/",
+});
+
+export default routes;

internal/gatsby/constants/templates.ts

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+import path from "path";
+
+const templates = Object.freeze({
+  categoriesTemplate: path.resolve("./src/templates/categories-template.tsx"),
+  notFoundTemplate: path.resolve("./src/templates/not-found-template.tsx"),
+  indexTemplate: path.resolve("./src/templates/index-template.tsx"),
+  tagsTemplate: path.resolve("./src/templates/tags-template.tsx"),
+  pageTemplate: path.resolve("./src/templates/page-template.tsx"),
+  postTemplate: path.resolve("./src/templates/post-template.tsx"),
+});
+
+export default templates;