Make --strict toggleable for mkdocs build

[CasperWA]

Fixes #77

Revert commit d525ea0.

Make the addition/usage of the --strict option toggleable according to a new warnings_as_errors boolean input.
By default, this is set to true and must explicitly be set to false.

If warnings_as_errors is set to false, a warning will be emitted in the Actions workflow run.

[daniel-sintef]

How would you use this in a downstream ci file? You can just link me to the documentation of how to use this

[daniel-sintef]

Looks good, I just want to know how to use it downstream :)

[CasperWA]

How would you use this in a downstream ci file? You can just link me to the documentation of how to use this

I would set the appropriate input parameter (warnings_as_errors) to the value one desires (true (default) for using warnings as errors; false for not doing so).
Updated documentation: https://github.com/SINTEF/ci-cd/blob/cwa/fix-77-undo-bad-change/docs/workflows/ci_tests.md#inputs-3
In raw format, and specifically: https://github.com/SINTEF/ci-cd/blob/cwa/fix-77-undo-bad-change/docs/workflows/ci_tests.md?plain=1#L119

An example of how to use the workflows in general is described in the general GitHub documentation (they're called "callable workflows") referenced in the main pages of the documentation as well as an example in each workflow-specific documentation page.
For the CI - Tests workflow, the example is here: https://github.com/SINTEF/ci-cd/blob/cwa/fix-77-undo-bad-change/docs/workflows/ci_tests.md#usage-example

[CasperWA]

In general, the documentation exists here: https://sintef.github.io/ci-cd

Here, you'll find this section "General usage": https://sintef.github.io/ci-cd/latest/#general-usage

[daniel-sintef]

Great, thanks!