Support pipe operator in onTypeFormatting

[renkun-ken]

Currently, we use a trick of appending a zero to complete a partial expression so that it is made stylizable by styler.

However, this trick no longer applies to the newly introduced pipe syntax in R 4.1 where it is syntactically incorrect to pipe to anything other than an explicit function call.

Previously if we hit "enter" in the end of the following line

1:10 %>%

then onTypeFormating will format the following code

1:10 %>%
0

with proper indention, it becomes

1:10 %>%
  0

But the same does not work with

1:10 |>
0

as it is not accepted by the parser.

Now styler has supported pipe expressions via r-lib/styler#803.