Update README

[ci skip]

Author: gaborcsardi

README.md

@@ -141,12 +141,14 @@ result <- run(px, "--help", echo = TRUE)
     #>   outln  <string>            -- print string to stdout, add newline
     #>   errln  <string>            -- print string to stderr, add newline
     #>   errflush                   -- flush stderr stream
-    #>   cat    <filename>          -- print file to stdout
+    #>   cat    <filename>          -- print file to stdout (use '<stdin>' for standard input)
     #>   return <exitcode>          -- return with exitcode
     #>   writefile <path> <string>  -- write to file
     #>   write <fd> <string>        -- write to file descriptor
     #>   echo <fd1> <fd2> <nbytes>  -- echo from fd to another fd
     #>   getenv <var>               -- environment variable to stdout
+    #>   rawout <hexstring>         -- write raw bytes (hex pairs) to stdout
+    #>   rawerr <hexstring>         -- write raw bytes (hex pairs) to stderr
 
 > Note: From version 3.0.1, processx does not let you specify a full
 > shell command line, as this involves starting a grandchild process
@@ -610,9 +612,10 @@ started running.
 p <- process$new("nonexistant-command-for-sure")
 ```
 
-    #> Error in c("process_initialize(self, private, command, args, stdin, stdout, ", : ! Native call to `processx_exec` failed
-    #> Caused by error in `chain_call(c_processx_exec, command, c(command, args), pty, pty_options, …`:
-    #> ! cannot start processx process 'nonexistant-command-for-sure' (system error 2, No such file or directory) @unix/processx.c:613 (processx_exec)
+    #> Error in `process_initialize()`:
+    #> ! ! Native call to `processx_exec` failed
+    #> Caused by error in `chain_call(...)`:
+    #> ! cannot start processx process 'nonexistant-command-for-sure' (system error 2, No such file or directory) @unix/processx.c:651 (processx_exec)
 
 ``` r
 p2 <- process$new(px, c("sleep", "1", "command-does-not-exist"))