(env/refactor): standardize .gitignore

- basically the same one I use in all my other libraries
  - I believe it's an old version of Node output from gitignore.io iirc
- it has comments unlike the old one, so that's much nicer for those
  who aren't totally sure what each entry is for

.gitignore

@@ -1,10 +1,28 @@
+### custom ###
+
+# build output
 build/
+# test coverage output
 coverage/
 
+### Node ###
+
+# Logs
+logs
+*.log
 npm-debug.log*
+
+# Dependency directories
 node_modules/
 
+# Optional npm cache directory
+.npm
+
+# Optional REPL history
+.node_repl_history
+
+# Output of 'npm pack'
 *.tgz
 
-.DS_Store
-*~
+# dotenv environment variables file
+.env