Unrevert prerelease fix, and fix release error (#4353)

* Reapply "Add "type" = "module" to ensure it is present (#4350)" (#4352)

This reverts commit 8214fd7.

* Mark prettier config file as CommonJS

I *think* this will fix a problem with the release process in which we saw an
error:

```
Error:  Invalid configuration for file "/home/runner/work/matrix-js-sdk/matrix-js-sdk/package.json":
Error:  module is not defined in ES module scope
Error:  This file is being treated as an ES module because it has a '.js' file extension and '/home/runner/work/matrix-js-sdk/matrix-js-sdk/package.json' contains "type": "module". To treat it as a CommonJS script, rename it to use the '.cjs' file extension.
```

Author: richvdh

.prettierrc.js renamed to .prettierrc.cjs

@@ -12,3 +12,6 @@ do
         jq ".$i = .matrix_lib_$i" package.json > package.json.new && mv package.json.new package.json && yarn prettier --write package.json
     fi
 done
+
+# Ensure that "type": "module" is present
+jq '.type = "module"' package.json > package.json.new && mv package.json.new package.json && yarn prettier --write package.json