[fluentd-elasticsearch] adding request timeout config

[harshavardhanc]

What this PR does / why we need it:

Adding reqeust timeout configuration variable. This is useful when Elasticsearch cannot return response for bulk request within the default of 5 seconds. https://github.com/uken/fluent-plugin-elasticsearch#request_timeout

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)

• fixes #

Special notes for your reviewer:

Checklist

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.]

• [x] DCO signed
• [x] Chart Version bumped (if the pr is an update to an existing chart)
• [x] Variables are documented in the README.md
• [x] Title of the PR starts with chart name (e.g. [fluentd-elasticsearch])

[request-info[bot]]

I am sure you can be more effusive ;-)

[harshavardhanc]

@monotek Used issue template and bumped up chart version.

[harshavardhanc]

@monotek Bumped up chart version to 9.3.0