add description of makeself option «target» (#307)

* add description of option target, see https://github.com/megastep/makeself/issues/306#issuecomment-1547649366

* https://github.com/megastep/makeself/pull/307#issuecomment-1548630300

README.md

diff --git a/README.md b/README.md
index 873426d..6984ca0 100644
--- a/README.md
+++ b/README.md
@@ -107,6 +107,7 @@
     * **`--lsm` _file_** : Provide a Linux Software Map (LSM) file to makeself, that will be embedded in the generated archive. LSM files are describing a software package in a way that is easily parseable. The LSM entry can then be later retrieved using the `--lsm` argument to the archive.
     * **`--tar-format opt`** : Specify the tar archive format (default is ustar); you may use any value accepted by your tar command (such as posix, v7, etc).
     * **`--tar-extra opt`** : Append more options to the tar command line.
+    * **`--target dir`** : Specify the directory where the archive will be extracted.
 
         For instance, in order to exclude the `.git` directory from the packaged archive directory using the GNU `tar`, one can use `makeself.sh --tar-extra "--exclude=.git" ...`