fix slideshow bug, initialized slides after the content is loaded

[aguyran]

Issue that this pull request solves

Closes: #428

Proposed changes

Brief description of what is fixed or changed

Assigned a empty this.deck and initialized with new Reveal object every time ngAfterView triggers, so it assigns relevant classes after every render

Types of changes

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• Bugfix (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 not work as expected)
• Documentation update (Documentation content changed)
• Other (please describe):

Checklist

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• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• My changes does not break the current system and it passes all the current test cases.

Screenshots

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Other information

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[goliakshay357]

Hello @aguyran,
LGTM!!. Feel free to check #431 #432

Thanks for the update :)