bug#34842: 26.1; Alist documentation: let-alist

[Sebastián Monía]

The macro let-alist is too useful to work with JSON-parsed data for it to be missing from the docs.

In the page https://www.gnu.org/software/emacs/manual/html_node/elisp/Association-Lists.html we should add some documentation about it. Below a suggestion.

Thank you!

— Macro: let-alist `value`

Creates a binding for each symbol in the association list `value`, prefixed with dot. This is very useful when accessing several items in the same alist, and it's best understood through a simple example:

(setq colors '((rose red) (lily white) (buttercup yellow)))

(let-alist colors

    (print .rose)

    (print .buttercup))

    ⇒ red

    ⇒ yellow

In GNU Emacs 26.1 (build 1, x86_64-w64-mingw32)

 of 2018-05-30 built on CIRROCUMULUS

Repository revision: 07f8f9bc5a51f5aa94eb099f3e15fbe0c20ea1ea

Windowing system distributor 'Microsoft Corp.', version 10.0.17134

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