Update immutable from 4.0.0-rc.12 to ^4.3.8

- Update immutable dependency to stable v4.3.8
- Add type assertions for getIn calls that now return unknown in v4 stable
- Add skipLibCheck to tsconfig.json for @nteract and @octokit .d.ts compat
- Add patch-package patch for @nteract/commutable .ts source files

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

tsconfig.json

@@ -23,6 +23,7 @@
     "jsx": "react",
     "moduleResolution": "node",
     "resolveJsonModule": true,
+    "skipLibCheck": true,
     "noEmit": true,
     "types": [
       "jest"