chore: use nix flakes with direnv

ericcrosson-bitgo · ericcrosson-bitgo · commit 8cb861b74aba · 2022-05-12T10:15:38.000-05:00
Requires a fairly recent version of nix (I'm on 2.8.0) and opting in
to the following experimental features:

```
nix-command flakes
```
diff --git a/.envrc b/.envrc
@@ -1 +1 @@
-use nix
+use flake
diff --git a/.gitignore b/.gitignore
@@ -1,6 +1,7 @@
+.direnv/
 .drone.yml
 .nyc_output/
+.turbo/
+coverage/
 dist/
 node_modules/
-coverage/
-.turbo/
