Support for multiple ligature'd fonts

Refactors the ligature configuration to support more than just Iosevka
(uses Fira Code as the second font).

modules/ui/pretty-code/autoload/autoload.el

@@ -0,0 +1,27 @@
+;;; ui/pretty-code/autoload.el -*- lexical-binding: t; -*-
+
+;;;###autoload
+(defvar +pretty-code-enabled-modes t
+  "List of major modes in which `prettify-symbols-mode' should be enabled.
+If t, enable it everywhere. If the first element is 'not, enable it in any mode
+besides what is listed.")
+
+
+;;;###autoload
+(defun +pretty-code|init-pretty-symbols ()
+  "Enabled `prettify-symbols-mode'.
+
+If the current major mode is disabled in `+pretty-code-enabled-modes', this
+function does nothing. Otherwise, it sets the value of
+`prettify-code-symbols-alist' according to `+pretty-code-symbols-alist' for the
+current major mode."
+  (when (or (eq +pretty-code-enabled-modes 't)
+            (if (eq (car +pretty-code-enabled-modes 'not))
+                (not (memq major-mode (cdr +pretty-code-enabled-modes)))
+              (memq major-mode +pretty-code-enabled-modes)))
+    (setq prettify-symbols-alist
+          (append (alist-get major-mode +pretty-code-symbols-alist)
+                  (default-value 'prettify-symbols-alist)))
+    (when prettify-symbols-mode
+      (prettify-symbols-mode -1))
+    (prettify-symbols-mode +1)))