wrap left and mid border config in style

[wvjgsuhp]

This is for users to config borders for left and mid elements like this,

-- proposed
mid = {
  border = { "│", " ", "│", "│", "│", " ", "│", "│" },
}

instead of,

-- current
mid = {
  border = { style = { "│", " ", "│", "│", "│", " ", "│", "│" } },
}

Otherwise, it should be specified in the doc.

[SmiteshP]

Actually I didn't intend for the end users to use array's to set the border characters. And just use the strings "single" "double" etc etc to set the border and let navbuddy handler the rest.

[wvjgsuhp]

Got it.
I found this while making something like this.

Also, didn't notice these changes would break the setting with "single", "double", etc.