Remove left_side container by default if there is no content

[huong-li-nguyen]

Description

• Remove left_side container by default if there is no content (e.g. single page, no dashboard title, no controls)

Screenshot

Example Code:

import os
import vizro.plotly.express as px
from vizro import Vizro
import vizro.models as vm

df = px.data.iris()

page = vm.Page(
    title="My first dashboard",
    components=[
        vm.Graph(id="scatter_chart", figure=px.scatter(df, x="sepal_length", y="petal_width", color="species")),
        vm.Graph(id="hist_chart", figure=px.histogram(df, x="sepal_width", color="species")),
    ],
)

dashboard = vm.Dashboard(pages=[page])

if __name__ == "__main__":
    Vizro._user_assets_folder = os.path.abspath("../assets")
    Vizro().build(dashboard).run()

Checklist

• I have not referenced individuals, products or companies in any commits, directly or indirectly
• I have not added data or restricted code in any commits, directly or indirectly
• I have updated the docstring of any public function/class/model changed
• I have added the PR number to the change description in the changelog fragment, e.g. Enable feature XXX ([#1](https://github.com/mckinsey/vizro/pull/1)) (if applicable)
• I have added tests to cover my changes (if applicable)

Types of changes

• Docs/refactoring (non-breaking change which improves codebase)
• 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)

Notice

• I acknowledge and agree that, by checking this box and clicking "Submit Pull Request":

  • I submit this contribution under the Apache 2.0 license and represent that I am entitled to do so on behalf of myself, my employer, or relevant third parties, as applicable.
  • I certify that (a) this contribution is my original creation and / or (b) to the extent it is not my original creation, I am authorised to submit this contribution on behalf of the original creator(s) or their licensees.
  • I certify that the use of this contribution as authorised by the Apache 2.0 license does not violate the intellectual property rights of anyone else.