Merge #17735

17735: examples/gcoap_dtls: Increase stack size r=maribu a=maribu

### Contribution description

As the title says. The stack size was copied over from `tests/pkg_tinydtls_sock_async` cargo-cult style. Also some typos in the README were fixed.

### Testing procedure

Previously on my Nucleo-F767ZI, the CoAP client triggered the MPU stack guard on sending the DTLS hello. With this, the board no longer crashes.

### Issues/PRs references

None

Co-authored-by: Marian Buschsieweke <marian.buschsieweke@ovgu.de>

examples/gcoap_dtls/Makefile

@@ -108,3 +108,4 @@ ifndef CONFIG_KCONFIG_MODULE_GCOAP
 GCOAP_RESEND_BUFS_MAX ?= 2
 CFLAGS += -DCONFIG_GCOAP_RESEND_BUFS_MAX=$(GCOAP_RESEND_BUFS_MAX)
 endif
+CFLAGS += -DTHREAD_STACKSIZE_MAIN=\(2*THREAD_STACKSIZE_LARGE\)

examples/gcoap_dtls/README.md

@@ -2,13 +2,13 @@
 
 This is an additional gcoap example, but with enabled DTLS. It only provides a
 custom configured makefile, while the code is a symlink to the original gcoap
-example. Therefore, the infos and usage notes of the other README also applies to this
-example.
+example. Therefore, the infos and usage notes of the other README also applies
+to this example.
 
-Please note, that with DTLS the default port is 5684 and not 5683, thus CoAP requests
-must be sent to this port.
+Please note, that with DTLS the default port is 5684 and not 5683, thus CoAP
+requests must be sent to this port.
 
-Since DTLS has higher memory and and ROM requirements, more boards are blacklisted
+Since DTLS has higher memory and ROM requirements, more boards are blacklisted
 for this example compared to the non-DTLS gcoap example.
 
 ### CoAP query with DTLS enabled