chore: Add direnv's .envrc and update BACKLOG.md

Author: juniorsundar

.envrc

@@ -1 +1,5 @@
+# shellcheck shell=bash
+if ! has nix_direnv_version || ! nix_direnv_version 3.1.0; then
+  source_url "https://raw.githubusercontent.com/nix-community/nix-direnv/3.1.0/direnvrc" "sha256-yMJ2OVMzrFaDPn7q8nCBZFRYpL/f0RcHzhmw/i6btJM="
+fi
 use flake

docs/BACKLOG.md

@@ -9,9 +9,9 @@
     - [x] RealVectorStateSpace
     - [x] SO2
     - [x] SO3
-    - [/] CompoundStateSpace
-        - [ ] SE2
-        - [ ] SE3
+    - [x] CompoundStateSpace
+        - [x] SE2
+        - [x] SE3
 - [x] Refactor Python Bindings module: `oxmpl-py`:
     - ~Its a mess right now...~
     - May revisit this later

flake.nix

@@ -60,7 +60,7 @@
 
           uv pip install pre-commit
           pre-commit install
-          zsh
+          # zsh
         '';
       };
     });