Fix typos and ports in contributing docs

[ilyatitovich]

This PR fixes a couple of small issues in the contributing docs:

• typo: lond-term → long-term
• incorrect port in localhost example

While reading the docs, I noticed that the instructions mention running fillFeedsWithPosts() from DevTools, but the function is not available on window in the current ESM setup.

I’d like to ask whether this is still the recommended way to populate feeds, or if the docs should be updated to reflect the current approach.

Motivation

Clear and accurate documentation helps reduce friction for new contributors.

[ai]

Thanks!