Please improve installation notes

[yuzumx]

Hello:

In you README:

(add-hook 'flycheck-mode-hook #'flycheck-rust-setup)

In some cases it seems unreliable.

My advice:

(with-eval-after-load 'rust-mode
    (add-hook 'flycheck-mode-hook #'flycheck-rust-setup))

Sorry for my poor English.

Thanks.

[fmdkdd]

I think I wrote it that way since users may use use-package or something else. But it may be best to provide more robust copy-and-paste instructions.

Fixed by 089330ac3bb49525ae6a8607a9ea978560ccf721

[yuzumx]

Thank you.