MINOR: [R][Documentation] Add default descriptions in CsvParseOptions…

…$create() docs (apache#37909)

### Rationale for this change

Add more function documentation for folks who want to manually change `quote_char` or `escape_char` options in `CsvParseOptions$create()`, as I did in apache#37908.

I had to go through the source code to arrow/r/R/csv.R - [line 587](https://github.com/apache/arrow/blob/7dc9f69a8a77345d0ec7920af9224ef96d7f5f78/r/R/csv.R#L587) to find the default argument, which was a pain.

### What changes are included in this PR?

Documentation changes

### Are these changes tested?

No - not changing underlying code. Maintainers might need to rebuild package to include these changes in man/ folder

### Are there any user-facing changes?

Yes, on documentation of methods.

Lead-authored-by: Angela Li <angela-li@users.noreply.github.com>
Co-authored-by: Nic Crane <thisisnic@gmail.com>
Signed-off-by: Nic Crane <thisisnic@gmail.com>

r/R/csv.R

@@ -404,10 +404,10 @@ CsvTableReader$create <- function(file,
 #'
 #' - `delimiter` Field delimiting character (default `","`)
 #' - `quoting` Logical: are strings quoted? (default `TRUE`)
-#' - `quote_char` Quoting character, if `quoting` is `TRUE`
+#' - `quote_char` Quoting character, if `quoting` is `TRUE` (default `'"'`)
 #' - `double_quote` Logical: are quotes inside values double-quoted? (default `TRUE`)
 #' - `escaping` Logical: whether escaping is used (default `FALSE`)
-#' - `escape_char` Escaping character, if `escaping` is `TRUE`
+#' - `escape_char` Escaping character, if `escaping` is `TRUE` (default `"\\"`)
 #' - `newlines_in_values` Logical: are values allowed to contain CR (`0x0d`)
 #'    and LF (`0x0a`) characters? (default `FALSE`)
 #' - `ignore_empty_lines` Logical: should empty lines be ignored (default) or