Update contributing guide for dev server

[stnguyen90]

What does this PR do?

Add step for creating .env file because without the file, npm run dev results in:

 VITE v3.2.1 ready in 568 ms
➜ Local: http://127.0.0.1:3000/
➜ Network: use --host to expose
window is not defined
ReferenceError: window is not defined
at /private/tmp/console/src/lib/stores/sdk.ts:16:61
at async instantiateModule (file:///private/tmp/console/node_modules/vite/dist/node/chunks/dep-d29b4e33.js:54234:9)
window is not defined
ReferenceError: window is not defined
at /private/tmp/console/src/lib/stores/sdk.ts:16:61
at async instantiateModule (file:///private/tmp/console/node_modules/vite/dist/node/chunks/dep-d29b4e33.js:54234:9)
window is not defined
ReferenceError: window is not defined
at /private/tmp/console/src/lib/stores/sdk.ts:16:61
at async instantiateModule (file:///private/tmp/console/node_modules/vite/dist/node/chunks/dep-d29b4e33.js:54234:9)

Add note about adblocker because this error occurs with adblocker enabled:

TypeError: Failed to fetch dynamically imported module: http://localhost:3000/.svelte-kit/generated/nodes/0.js

Test Plan

Manual

Related PRs and Issues

None

Have you read the Contributing Guidelines on issues?

Yes

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Name	Status	Preview	Updated
console	✅ Ready (Inspect)	Visit Preview	Dec 16, 2022 at 5:19PM (UTC)