Fix README to reflect devtools v2.0.1

- "devtools" v2.0.1 mixed up the logic for "dontrun" examples (see https://github.com/r-lib/devtools/issues/2003); until this is fixed, use `devtools::run_examples(run = FALSE)`

- Note: revert this commit once devtools issue 2003 is fixed

README.md

@@ -199,7 +199,10 @@ You can contribute to this project in different ways:
     note: you may need to compile dynamic libraries first with
     `pkgbuild::compile_dll()`.
   * Ideally, add examples to function documentation and check these examples
-    with the command `devtools::run_examples()`
+    with the command `devtools::run_examples()`.
+    Note: "devtools" v2.0.1 mixed up the logic for "dontrun" examples (see
+    https://github.com/r-lib/devtools/issues/2003); until this is fixed,
+    use `devtools::run_examples(run = FALSE)`.
   * Ideally, expand and/or add vignettes.
 
 
@@ -278,6 +281,9 @@ You can contribute to this project in different ways:
        ```{r}
        devtools::run_examples()
        ```
+       Note: "devtools" v2.0.1 mixed up the logic for "dontrun" examples (see
+       https://github.com/r-lib/devtools/issues/2003); until this is fixed,
+       use `devtools::run_examples(run = FALSE)`.
 
     1. Run tests as if not on CRAN, in an interactive R session,
        and with a sequential schedule.