feat(version-control): add github-review package

This serves as a alternative to the code-review package. I'm adding it
mostly for testing purposes so I can compare the two and see the
pros/cons with each.

modules/version-control/siren-github-review.el

@@ -0,0 +1,17 @@
+;;; siren-github-review.el --- jimeh's Emacs Siren: github-review configuration
+
+;;; Commentary:
+
+;; Basic configuration for github-review.
+
+;;; Code:
+
+(use-package github-review
+  :defer t
+  :custom
+  (github-review-fill-column 80)
+  (github-review-lgtm-message "lgtm :)")
+  (github-review-new-buffer-window-strategy 'switch-to-buffer))
+
+(provide 'siren-github-review)
+;;; siren-github-review.el ends here