add note for kubernetes constraints/nodeSelectors

[robertgroh]

Description

The Kubernetes operator faas-netes expects the constraints / nodeSelectors in the format <label-key>=<label-value>.

References:

• Pull Request (Node selector support via constraints #77), which introduced the feature
• the source code for the createSelector function, see how the key-value pair is split
• an issue regarding the difference between constraints for Docker Swarm & Kubernetes

also remove some erroneous white space in an URL, which broke the link and anchor

Motivation and Context

Clarify the constraints format for different container orchestrators, as this is stumbling block for some users, see openfaas/faas-netes #406: Help needed with constraints

How Has This Been Tested?

I looked over the rendered markdown.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Improve Documentation

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have signed-off my commits with git commit -s

[alexellis]

Thanks for the PR. We do need to remove those references to Swarm, it seems like a good time to do that.

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If you could squash your two commits down, I'll try to get this merged when I get the follow-up notification.

Given that the use-case sounds like work/commercial, do checkout the GitHub Sponsors options that we have for individual practitioners like yourself.

Alex