Conditionally activate `helm-bibtex` based on AUCTeX's `LaTeX-mode`.

[Hongyi Zhao]

Hi here,

I'm using the following configuration for `helm-bibtex`:

;;;;; begin configuration
(use-package helm
  :demand t
  :config (require 'helm-autoloads))
(use-package helm-bibtex
  :demand t
  :init
  (setq
   ;;https://github.com/tmalsburg/helm-bibtex#insert-latex-cite-commands
   bibtex-completion-cite-prompt-for-optional-arguments nil)

  :bind-keymap
  ("<menu>" . helm-command-prefix)
  :bind
  (
   :map helm-command-map
   ("b" . helm-bibtex)
   ("B" . helm-bibtex-with-local-bibliography)
   ("n" . helm-bibtex-with-notes)
   ("<menu>" . helm-resume)
   )
  )
;;;;; end configuration

The above configuration will always enable the above packages during
the starting process of Emacs, but I want to conditionally activate
`helm-bibtex` based on AUCTeX's `LaTeX-mode` is called and enabled.
Any tips for achieving this goal?

Regards,
Zhao
-- 
Assoc. Prof. Hongsheng Zhao <hongyi.zhao@gmail.com>
Theory and Simulation of Materials
Hebei Vocational University of Technology and Engineering
No. 473, Quannan West Street, Xindu District, Xingtai, Hebei province