Enable numeric input for particular scales

[cromanpa94]

Allow users to define their particular scale level

[rog-SARTHAK]

commit 25ac4b7

Addressed in commit 83596e8

Steps:

Made UI function changes for a Custom box

custom text

  conditionalPanel(
    condition = "input.scale == 'custom'",
    textInput("custom_scale", "Enter a custom scale", value=3)
  )

Modified if else statement in observe function.

Set setView of observe function to be the only setView.