Fix range formatting handling initial indentation

[renkun-ken]

Closes #264.

If the selection range has non-zero indentation, then a apply_initial_indention function injected to the formatting styles so that the top level expressions get the indentation.

For example, to format the code inside the the following function

my_fun <- function() {
  data <- query(
    con ,
    "select name, group, max(update_time) as max_time
from users
where date = ?date
group by group",
date = 20200601
  )
x = 2
y = 3  
}

the code will be enclosed inside { ... } and then apply_initial_indention will apply the indention to all top-level expressions of the selection, then the curly braces are droped to get the formatted text.

The result is like

my_fun <- function() {
  data <- query(
    con,
    "select name, group, max(update_time) as max_time
from users
where date = ?date
group by group",
    date = 20200601
  )
  x = 2
  y = 3
}

[randy3k]

it doesn't work with tabs unfortunately. Though it seems that styler doesn't support tabs r-lib/styler#347

[renkun-ken]

Yes, it does not support tabs. So I just ignore this case unless somebody complains.

[randy3k]

LGTM. Please merge after the tests pass.