Update social media handbook: "provide details"

Adding extra point to Social Media Guidelines Handbook: "**provide details**"

@sytses there we go, as you asked over the chat. Is that explained well enough? 

cc/ @ashleys @amara

See merge request !2446

Update "/contributing/" page

### What?

1. Linking '[community writers](https://about.gitlab.com/community/writers/)' page from '[contributing](https://about.gitlab.com/contributing/)' page
2. Removing "Pull" requests

### Why?

1. The "community writers" page isn't linked to any other page within about.GitLab.com
2. Pull requests aren't being accepted anymore from the GitHub mirror.

cc/ @axil @amara @afolson 
 


See merge request !2447

Add more promises inspired by https://news.ycombinator.com/item?id=11977129



See merge request !2448

Support handbook updates

* Fix link to internal issue tracker, move to support tracker
* Resize zendesk images

See merge request !2437

Tips on searching for errors and using Sentry

/cc: @dblessing 

See merge request !2395

Specify MR minibosses



See merge request !2452

Release 8.9.1

See merge request !2449

Fix nicknames, and add instruction on it

Made nicknames for a few team members consistent; (specifically @twk3 @xyzzy ), added a guideline on it as part of the guide on how to add yourself to the team page. 

I then moved that entire instruction page to the handbook/general-onboarding page, because it did not make sense to me that it was a dangling file at the top level of the repo.

\cc @brittanyr 

See merge request !2426

clarify directory

Just a tad more detail.

See merge request !2445

Add release category where missing



See merge request !2442

Make the list of categories the same as the archives



See merge request !2441

Add the release category to all release blog posts

This will enable a category of releases under
https://about.gitlab.com/blog/categories/release

See merge request !2440

Update off boarding for engineering



See merge request !2435

Speedy meetings preference

As requested by @sytses; set our calendar preferences to "speedy meetings" making meetings 5 or 10 minutes shorter to leave some time for writing down notes etc. 

See merge request !2438

Fix handbook index page list



See merge request !2439

effected -> affected since the latter is the right verb for this case



See merge request !2419

Added file lock tile to pricing page

[What do we think?](/uploads/2cb9a39c0a9c33b1b5faa1436c070b5f/screencapture-localhost-4567-pricing-1466755257802.png)

cc. @amara @lukebabb 

Closes #715 

See merge request !2434

Blog Post - "Secure GitLab Pages with StartSSL"

Blog Post - ~~Guest Writers program~~

Outlines, objective, further comments - view blog-posts#202

Cover image:  https://unsplash.com/photos/sseiVD2XsOk

- [x] Technical review - @axil 
- [x] Final review - @amara 
- [x] Change date/time

See merge request !2028

Merge branch 'master' of https://gitlab.com/gitlab-com/www-gitlab-com into virtuacreative-startssl-post