Add support for CA bundles (#885)

Why:

- Allow CA cert bundles to be used

This change addresses the need by:

- Adding a constructor that takes a pointer to the bundle
- Setting the WiFiClientSecure to use the bundle
- Adding an example

examples/esp32_pio/WebSocketClientSSLBundle/run_gen_script.py

@@ -0,0 +1,6 @@
+Import("env")
+
+env.Execute("$PYTHONEXE -m pip install cryptography")
+env.Execute("$PYTHONEXE gen_crt_bundle.py --input cacrt_all.pem")
+env.Execute("mkdir -p data/cert")
+env.Execute("mv -f x509_crt_bundle data/cert/x509_crt_bundle.bin")