added keep-going flag to build-docs

[Celsuss]

NOTE: Kedro datasets are moving from kedro.extras.datasets to a separate kedro-datasets package in
kedro-plugins repository. Any changes to the dataset implementations
should be done by opening a pull request in that repository.

Description

MR for issue #3132
Added the --keep-trying flag to build-docs.sh (which is called by make build-docs).
Because of the W flag any warning is treated as an error, with the --keep-going flag the build will finish despite the warnings turned error.

Development notes

All that was changed was an added flag to build-docs.sh.
I have tried running the make build-docs

Checklist

• Read the contributing guidelines
• Signed off each commit with a Developer Certificate of Origin (DCO)
• Opened this PR as a 'Draft Pull Request' if it is work-in-progress
• Updated the documentation to reflect the code changes
• Added a description of this change in the RELEASE.md file
• Added tests to cover my changes
• Checked if this change will affect Kedro-Viz, and if so, communicated that with the Viz team

[Celsuss]

I noticed that I messed up a thing with the commits. had t create a new MR to fix it that can be found here: #3140