Prettifies any input and show a placeholder in case the value is nil.

Examples

iex> Backpex.HTML.pretty_value(nil)
"—"

iex> Backpex.HTML.pretty_value("")
"—"

iex> Backpex.HTML.pretty_value(1_000_000)
1000000

iex> Backpex.HTML.pretty_value(1.11)
1.11

iex> Backpex.HTML.pretty_value("Hello, universe")
"Hello, universe"