[nix] Add jq tool to dev shell

Summary:
Adds [[ https://jqlang.org/ | jq ]] to nix dev shell. It's useful for manipulating JSON in CLI.
It's also needed for the script added in the next diff

Test Plan:
```
# none or e.g. homebrew if installed globally
which jq

nix develop
which jq
# now it shows nix path
```

Reviewers: ashoat, kamil, tomek, O1 Nix

Reviewed By: ashoat

Differential Revision: https://phab.comm.dev/D14403

Author: barthap

nix/dev-shell.nix

@@ -20,6 +20,7 @@
 , fmt
 , glog
 , grpc
+, jq
 , libiconv
 , libuv
 , localstack
@@ -54,6 +55,7 @@ mkShell {
     # generic development or tools
     arcanist
     awscli2
+    jq
     shellcheck
     sops
     terraform