docs:: Update GSoC application tips.
docs:: Update GSoC application tips.

- Add missing link for GitHub.
- Fix broken links to Matt Ringel's blog post.
- Add link to Julia Evans blog post.
- Add section heading for "Questions Are Important."
- Rearrange some content to fit with new section heading.

With additional tweaks from tabbott:
* Avoid linking to chat.zulip.org not via our documentation.
* Avoid the CZO abbreviation.

zulip/zulip,andersk/zulip,rht/zulip,zulip/zulip,andersk/zulip,eeshangarg/zulip,eeshangarg/zulip,kou/zulip,kou/zulip,rht/zulip,eeshangarg/zulip,zulip/zulip,rht/zulip,eeshangarg/zulip,zulip/zulip,kou/zulip,andersk/zulip,kou/zulip,zulip/zulip,rht/zulip,rht/zulip,andersk/zulip,andersk/zulip,kou/zulip,kou/zulip,rht/zulip,kou/zulip,zulip/zulip,rht/zulip,andersk/zulip,eeshangarg/zulip,eeshangarg/zulip,andersk/zulip,zulip/zulip,eeshangarg/zulip