Integrate Blazor Repl in documentation

[jivanova]

• Deadline for design - 24 Sept https://github.com/telerik/kendo-ux-private/issues/332
• Deadline for giving instructions of Blazor Repl ( hosting & passing snippet in header functionality ) - 24th September https://github.com/telerik/blazor/issues/2953
• Implementation in docs-seed

Requirements

Based on the Blazor Repl instruction, we might be able to deliver live editing capabilities and will sync the requirements. Until then, the requirements are for integrating tabstrip and Open with Repl functionality.

• Add iframe for live editing https://telerik.blazorrepl.com/repl/
• Add tabstrip layout with Code
• [TBD by design] Layout in tabstrip
• [TBD by design] Add button that gets the code snippet and send it to blazor repl (https://github.com/telerik/docs-seed/blob/master/_assets/js/dojo.js#L10)
• Config.yml instructions for enabling feature => ex: enable_repl analogical to enable_dojo

[pepinho24]

postMessage API details: https://github.com/telerik/blazor-repl/issues/4

[pepinho24]

To enable adding REPL to code snippets, you need to add enable_blazorRepl: true in the _config.yml file.

With 46e4a47 commit, certain snippets can be skipped from adding the REPL buttons.

To do that, add a <div class="skip-repl"></div> right before the snippet. Example:

<div class="skip-repl"></div>
````C#
var foo= 5;
````
````VB.NET
Dim foo = 5
````

some text
some other text

<div class="skip-repl"></div>
````C#
var skipRepl = true
````