docs: update contributing

Author: ije

CONTRIBUTING.md

@@ -21,17 +21,14 @@ You will need [Deno](https://deno.land/) 1.7+.
 7. Marge to master branch by our maintainers.
 
 ```bash
-# set dev env
-echo 'ALEPH_DEV_PORT=2020' > .env.local
-
 # ssr/development with HMR
-deno run -A --unstable cli.ts dev ./examples/hello-world -L debug
+ALEPH_DEV_PORT=2020 deno run -A --unstable cli.ts dev ./examples/hello-world -L debug
 
 # ssr/production
-deno run -A --unstable cli.ts start ./examples/hello-world -L debug
+ALEPH_DEV_PORT=2020 deno run -A --unstable cli.ts start ./examples/hello-world -L debug
 
 # ssg
-deno run -A --unstable cli.ts build ./examples/hello-world -L debug
+ALEPH_DEV_PORT=2020 deno run -A --unstable cli.ts build ./examples/hello-world -L debug
 
 # run all tests
 deno test -A --unstable --location=https://deno.land/x/aleph