Docs: clarify varSelectInput() purpose and fix typo (#4391)

Explain that `varSelectInput()` is a `selectInput()` convenience wrapper
that returns the selected column name as a symbol for use with tidy
evaluation, and use plain `selectInput()` when a symbol is not needed.
Also fix the "to instead of" -> "instead of" typo in the existing
description of selectize.js.

Fixes #2334

Author: samuelbharti

NEWS.md

@@ -44,6 +44,10 @@
 
 * `need()` now gives a clearer error when called without either a `message` or `label` argument, instead of the cryptic "argument \"label\" is missing, with no default". (thanks @chasemc and @sundrelingam, #2509)
 
+* Clarified `varSelectInput()` documentation to explain that the input
+  returns a symbol for use with tidy evaluation, and fixed a grammatical
+  typo. (#2334)
+
 # shiny 1.13.0
 
 ## New features

R/input-select.R

@@ -304,9 +304,15 @@ selectizeScripts <- function() {
 #' Create a select list that can be used to choose a single or multiple items
 #' from the column names of a data frame.
 #'
+#' `varSelectInput()` is a convenience wrapper around [selectInput()] for use
+#' with tidy evaluation: it returns the selected column name as a symbol
+#' (see "Server value" below) so the value can be spliced directly into
+#' tidy-evaluation contexts without wrapping it in [rlang::sym()]. If you
+#' don't need a symbol, use [selectInput()] instead.
+#'
 #' By default, `varSelectInput()` and `selectizeInput()` use the
 #' JavaScript library \pkg{selectize.js}
-#' (<https://selectize.dev/>) to instead of the basic
+#' (<https://selectize.dev/>) instead of the basic
 #' select input element. To use the standard HTML select input element, use
 #' `selectInput()` with `selectize=FALSE`.
 #'