[IMP] bundling: Improve owl bundling process and output (#751)

The bundle pipeline can use a bit of a improvement:

Most of the process is moved from npm scripts to rollup.
Add package keys to smooth out the use of bundlers of the end users.
(Rollup by example check amongst others the main, module and browser key
to import the right version of a lib when needed).
Refactor rollup logic to make it more modular.
Add bundled module formats.
Add comments to tsconfig to see more clearly what's possible.
Add reference tag to help @types discovery in test files.

Co-authored-by: Simon Genin (ges) <ges@odoo.com>

.gitignore

@@ -26,4 +26,6 @@ node_modules
 # Extras temp file
 /tools/owl.js
 
-release-notes.md
+release-notes.md
+
+.rpt2_cache