Setup git-secret

This morning I'm attempting to secure my monorepo. How?

- `git secret`:  DONE: To version-control sensitive data
- `git secrets`: TODO: Lint code for sensitive data

I will probably update the CI to call `git secrets --scan` or some similar
command to fail when that exists non-zero. I have much to learn, but doing is
the best way to learn it.

.gitignore

@@ -31,3 +31,5 @@ node_modules/
 /configs/.config/fish/fish_variables
 /website/blog/public/
 /emacs/.emacs.d/tramp
+.gitsecret/keys/random_seed
+!*.secret