Switch to Changesets-based release process (#118)

* Switch to Changesets-based release process

* Bump version

* drop unused variable

* Update .github/workflows/version-or-publish.yml

Co-authored-by: Nicola Molinari <nicola.molinari@commercetools.com>

* Push also to a release line branch when releasing

* Change node version used in the version-or-publish workflow

* Switch to using the local action

Co-authored-by: Nicola Molinari <nicola.molinari@commercetools.com>

* build the action before trying to use it the workflow

* Add changeset and actually setup Changesets, lol

Co-authored-by: Nicola Molinari <nicola.molinari@commercetools.com>

scripts/version.js

@@ -0,0 +1,19 @@
+const fs = require("fs");
+const path = require("path");
+const { exec } = require("@actions/exec");
+
+process.chdir(path.join(__dirname, ".."));
+
+(async () => {
+  await exec("changeset", ["version"]);
+
+  const releaseLine = `v${require("../package.json").version.split(".")[0]}`;
+
+  const readmePath = path.join(__dirname, "..", "README.md");
+  const content = fs.readFileSync(readmePath, "utf8");
+  const updatedContent = content.replace(
+    /changesets\/action@[^\s]+/g,
+    `changesets/action@${releaseLine}`
+  );
+  fs.writeFileSync(readmePath, updatedContent);
+})();