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/platformio.ini

@@ -0,0 +1,25 @@
+; PlatformIO Project Configuration File
+;
+;   Build options: build flags, source filter
+;   Upload options: custom upload port, speed and extra flags
+;   Library options: dependencies, extra library storages
+;   Advanced options: extra scripting
+;
+; Please visit documentation for the other options and examples
+; https://docs.platformio.org/page/projectconf.html
+
+[env:esp32dev]
+platform = espressif32
+board = esp32dev
+framework = arduino
+monitor_speed = 115200
+upload_speed = 921600
+build_flags = 
+    -DCORE_DEBUG_LEVEL=5
+lib_deps = ../../../src
+
+extra_scripts = 
+    pre:run_gen_script.py
+
+board_build.embed_txtfiles = 
+    data/cert/x509_crt_bundle.bin