(dolist (frame (frame-list))
  (dolist (fontset (fontset-list))
    (set-fontset-font fontset 'unicode (font-spec :family "Segoe UI Emoji" :registry "iso10646-1") frame 'append)
    (set-fontset-font fontset 'unicode (font-spec :family "XITS Math":registry "iso10646-1") frame 'append)))

(setq-default prettify-symbols-alist '(("=>" . 8658) (":=" . 8796)))