build: decouple typegen/docgen from yarn build:lib (#1038)

* chore(deps-dev): upgrade sveld to v0.13.1

* build: separate sveld into a separate build script

* docs(contributing): update guideline on re-building docs

scripts/build-docs.js

@@ -0,0 +1,20 @@
+const { sveld } = require("sveld");
+const pkg = require("../package.json");
+
+sveld({
+  glob: true,
+  markdown: true,
+  markdownOptions: {
+    onAppend: (type, document, components) => {
+      if (type === "h1")
+        document.append(
+          "quote",
+          `${components.size} components exported from ${pkg.name}@${pkg.version}.`
+        );
+    },
+  },
+  json: true,
+  jsonOptions: {
+    outFile: "docs/src/COMPONENT_API.json",
+  },
+});