[AssetMapper] Adding notes about global variables and tailwind-bundle

[weaverryan]

Hi!

2 notes added for asset mapper:

• 1. A note about jQuery and global variables. This is the same as how things work in WebpackEncore, but there was a question about it recently - jQuery & AssetMapper symfony#50733 (comment)
• 2. Linked to the new https://github.com/SymfonyCasts/tailwind-bundle which makes Tailwind integration much easier. Apart from it being super new, I think this should be "the" way to add Tailwind vs the way described (which is much more work for no benefit).

Thanks!

[javiereguiluz]

Thank you Ryan.