[Wiki] Add "How to contribute" to developer wiki

[asfimport]

The website describes:

Interested in contributing? Join the mailing list or check out the developer wiki.

But I could not find "How to contribute" on the Wiki.

Though I can find it in the repository:

• https://github.com/apache/arrow#how-to-contribute

• https://github.com/apache/arrow/blob/master/.github/CONTRIBUTING.md#how-to-contribute-patches

  We can add the contents to find "How to contribute" more easily.
  Or, we can unify duplicated contents to the Wiki.

Reporter: okkez / @okkez
Assignee: Wes McKinney / @wesm

_{Note: This issue was originally created as ARROW-3066. Please see the migration documentation for further details.}

[asfimport]

Wes McKinney / @wesm:
We should add a contributor guide to the wiki. I can give you edit permissions if you give me your confluence username.

The developer wiki is useful right now because it shows the various projects and there are some JIRA dashboards that help see only issues related to particular subprojects

[asfimport]

okkez / @okkez:

We should add a contributor guide to the wiki. I can give you edit permissions if you give me your confluence username.

My confluence username is "okkez".

[asfimport]

Wes McKinney / @wesm:
OK, you should be able to edit the wiki now

[asfimport]

okkez / @okkez:
Thank you!
I will work for this in this week.

[asfimport]

Wes McKinney / @wesm:
This is now part of the main documentation site. I updated https://cwiki.apache.org/confluence/display/ARROW/Contributing+to+Apache+Arrow