Issue #39 - Add .asf.yaml for asf-site

[martin-g]

Which issue does this PR close?

Issue #39 .

Rationale for this change

To auto-update the documentation whenever something is pushed to the asf-site branch.

What changes are included in this PR?

Adds publish section in .asf.yaml so that it publishes to https://arrow.apache.org/datafusion-python

Are there any user-facing changes?

No

[martin-g]

Related-to: #104

[martin-g]

@kou Please review!

[kou]

We don't need this because we don't use Jira.

[martin-g]

Removed it!

[kou]

+1

[kou]

Oh, sorry. This pull request was closed...
We need to put .asf.yaml to the default branch (master) not asf-site.
I changed the base branch to master then this pull request was closed...
Could you create one more pull request that uses master as the base branch?

[kou]

Sorry... I was wrong...
We need to put .asf.yaml to asf-site... Could you create the same pull request again? Sorry...

https://cwiki.apache.org/confluence/display/INFRA/Git+-+.asf.yaml+features#Git.asf.yamlfeatures-Publishingabranchtoyourprojectwebsite

Note: although publishing the asf-site branch used to work without .asf.yaml being present, since May 2021 that file MUST be present at the root of the branch you wish to publish. for everything (including soft purging the CDN cache on updates) to work correctly.