Add CI script to switch the js-sdk into 'release mode'

So we can check the types still work against a released js-sdk

scripts/ci/js-sdk-to-release.sh

@@ -0,0 +1,21 @@
+#!/bin/sh
+
+# This changes the js-sdk into 'release mode', that is:
+# * The entry point for the library is the babel-compiled lib/index.js rather than src/index.ts
+# * There's a 'typings' entry referencing the types output by tsc
+# We do this so we can test that each PR still builds / type checks correctly when built
+# against the released js-sdk, because if you do things like `import { User } from 'matrix-js-sdk';`
+# rather than `import { User } from 'matrix-js-sdk/src/models/user';` it will work fine with the
+# js-sdk in development mode but then break at release time.
+# We can't use the last release of the js-sdk though: it might not be up to date enough.
+
+cd node_modules/matrix-js-sdk
+for i in main typings
+do
+    lib_value=$(jq -r ".matrix_lib_$i" package.json)
+    if [ "$lib_value" != "null" ]; then
+        jq ".$i = .matrix_lib_$i" package.json > package.json.new && mv package.json.new package.json
+    fi
+done
+yarn run build:compile
+yarn run build:types