fix: general polish

[ci skip]

Author: tegefaulkes

README.md

@@ -13,6 +13,25 @@ npm install --save @matrixai/exec
 
 ## Usage
 
+exec can be used in the following way.
+
+```ts
+import { exec } from '@matrixai/exec';
+// This should output the current enviroment while adding `test_env` to it.
+exec.execvp(
+  'node',
+  [
+    '-e',
+    'console.log(process.env)',
+  ],
+  {
+    test_env: 'this value'
+  },
+);
+```
+
+Note that only linux and mac platforms are supported.
+
 ## Development
 
 Run `nix develop`, and once you're inside, you can use:

package-lock.json

@@ -45,7 +45,7 @@ pub fn execvp(cmd: String, argv: Array, envp: Object) -> napi::Result<()> {
   for key in keys.iter() {
     let value = match envp.get::<String, String>(key.clone()) {
       Ok(Some(value)) => Ok(value),
-      Ok(None) => panic!("asd"),
+      Ok(None) => continue,
       Err(e) => Err(e),
     }.or_else(
       |e| Err(napi::Error::from_reason(e.to_string()))