Added host container query param to designer site

[J. Diego Rodríguez Royo (Diegorro98)]

Description

This PR allows to set a host container by using a query param. This query param should be a number that represents the index on CardDesigner._hostContainers array (and the index at Host App Choice Picker at the designer's UI).

To do that I created a function that checks that the index is on the valid range and then applies it.

How Verified

How you verified the fix, including one or all of the following:

1. New unit tests that were added if any. If none were added please add a quick line explaining why not.
   No tests were added, I didn't know where are CardDesigner class tests.

I was able to test that the query param works with this url: https://adaptivecards.io/designer?hostContainerIndex=1 but I wasn't able to make work the designer because although I tried to set up the development environment with this instructions and this workaround

Microsoft Reviewers: Open in CodeFlow

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Hi J. Diego Rodríguez Royo (@Diegorro98). This pull request has had no recent activity for the past 5 days . Please take the necessary actions (review, address feedback or commit if reviewed already) to move this along.

[microsoft-github-policy-service]

Hi J. Diego Rodríguez Royo (@Diegorro98). This pull request has had no recent activity for the past 5 days . Please take the necessary actions (review, address feedback or commit if reviewed already) to move this along.

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Staleness reset by anna-dingler

[microsoft-github-policy-service]

Hi J. Diego Rodríguez Royo (@Diegorro98). This pull request has had no recent activity for the past 5 days . Please take the necessary actions (review, address feedback or commit if reviewed already) to move this along.

[microsoft-github-policy-service]

Hi J. Diego Rodríguez Royo (@Diegorro98). This pull request has had no recent activity for the past 5 days . Please take the necessary actions (review, address feedback or commit if reviewed already) to move this along.

[microsoft-github-policy-service]

Hi J. Diego Rodríguez Royo (@Diegorro98). This pull request has had no recent activity for the past 5 days . Please take the necessary actions (review, address feedback or commit if reviewed already) to move this along.

[J. Diego Rodríguez Royo (Diegorro98)]

Closing this PR because I made a new PR (#8850) with more query params.