Fix CI warnings: add jsonlite dep, flush.console import, Rd docs

- Add jsonlite to Imports (used by beep() webhook)
- Add importFrom(utils, flush.console) to NAMESPACE
- Update na_sum.Rd to include quiet parameter
- Create beep.Rd documentation

man/na_sum.Rd

@@ -4,10 +4,14 @@
 \alias{na_sum}
 \title{Sum a numeric that contains missing values and ignore missing values}
 \usage{
-na_sum(x)
+na_sum(x, quiet = FALSE)
 }
 \arguments{
 \item{x}{a numeric vector}
+
+\item{quiet}{Logical. If \code{TRUE} (default \code{FALSE}), suppress the warning
+message. Useful when calling \code{na_sum()} inside a loop or \code{dplyr} pipeline
+where the message would be emitted repeatedly.}
 }
 \value{
 the sum, ignoring any missing values
@@ -18,4 +22,5 @@ Sum a numeric that contains missing values and ignore missing values
 \examples{
 x <- c(2, NA, 4, 9)
 na_sum(x) # 15
+na_sum(x, quiet = TRUE) # 15 (no message)
 }