Default routing (mars#145)

Runtime vars compatibility with split bundles (mars#133)

* Runtime vars compatibility with split bundles

* 📚 split bundle compatibility

* Upgrade inner buildpack for split bundle compatibility

📚 notices about CRA 2 incompatibility

Support dyno metadata during build (mars#129)

Update README with latest release tag (mars#126)

Update README with latest release tag

Support for custom bundle location via `JS_RUNTIME_TARGET_BUNDLE` (ma…

…rs#117)

* Support for custom bundle location via `JS_RUNTIME_TARGET_BUNDLE`

* 📚 about custom bundle location

* 📚 how to unset custom bundle path

* Upgrade to inner buildpack with improved custom bundle UX

Support for npm Private Modules (mars#96)

📚 fix typo

📚 revs to Proxy & Testing sections

📚 link to Architecture from Purpose