Add support for AD5706R

Add ad5706r.py driver
Add test script, example code
Update index.rst, init.py, supported_parts.md files
Add xml emu context file
Update hardware_map.yml file for test emulation

Signed-off-by: SGudla <Saikiran.Gudla@analog.com>

Author: SaikiranGudla

adi/__init__.py

@@ -24,6 +24,7 @@
 from adi.ad4858 import ad4858
 from adi.ad5592r import ad5592r
 from adi.ad5686 import ad5686
+from adi.ad5706r import ad5706r
 from adi.ad5710r import ad5710r
 from adi.ad5754r import ad5754r
 from adi.ad5940 import ad5940