[Cookbook][Assetic] Fix "javascripts" tag name typo
Move note about "javascripts" and "stylesheets" blocks to separate note blocks
minor #3485 [Cookbook][Assetic] Fix "javascripts" tag name typo (bicpi)

This PR was merged into the 2.3 branch.

Discussion
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[Cookbook][Assetic] Fix "javascripts" tag name typo

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | -

Maybe the following note *This will most commonly live in the ``javascripts`` block...* is a bit confusing because the example does not show this Twig block and it has the same name as the Twig tag... The note could either be removed or I could add the `javascripts` Twig block to clarify?

Commits
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f9a287b Move note about "javascripts" and "stylesheets" blocks to separate note blocks
cf8064d [Cookbook][Assetic] Fix "javascripts" tag name typo