feat: add proxy support (#102)

Adds support for the following environment variables:

- `https_proxy`
- `HTTPS_PROXY`
- `http_proxy`
- `HTTP_PROXY`
- `no_proxy`
- `NO_PROXY`

main.js

@@ -31,8 +31,6 @@ const skipTokenRevoke = Boolean(
   core.getInput("skip-token-revoke") || core.getInput("skip_token_revoke")
 );
 
-const baseUrl = core.getInput("github-api-url").replace(/\/$/, "");
-
 main(
   appId,
   privateKey,
@@ -40,7 +38,7 @@ main(
   repositories,
   core,
   createAppAuth,
-  request.defaults({ baseUrl }),
+  request,
   skipTokenRevoke
 ).catch((error) => {
   /* c8 ignore next 3 */