Refactor small annoyances with current code

[thiagomajesk]

• Moves Swish.Dialog.Transitions to /dialog (following the same pattern as in Add toasts API #3)
• Removes hidden trailing whitespace from docs that prevented correct formatting
• Passes attrs directly to Dialog.new function (following the same pattern as in Add toasts API #3)
• Fixes Dialog not accepting custom ids
• Introduces Swish.EL module with some useful helpers that allows:
  • Unifying element id template generation (always positive and not necessarily increasing)
  • Automatically extracting and scaping id from components that can have an id