Add sram_config example to documentation

docs/source/basic_usage.md

@@ -39,9 +39,27 @@ openram.init_openram("myconfig.py") # Config files are explained on this page
 from openram import tech
 ...
 ```
+
 Note that you should need to initalize OpenRAM so that the modules are imported properly. You can also look
 at [sram_compiler.py](../../sram_compiler.py) as an example on how to use "openram."
 
+If you want to pass custom configuration when generating an SRAM, you can use `sram_config` class.
+```python
+import openram
+openram.init_openram("myconfig.py")
+openram.setup_bitcell()
+
+from openram.modules import sram_config
+c = sram_config(...)
+
+from openram.modules import sram
+s = sram(sram_config=c,
+         name="custom_name")
+
+s.save()
+
+openram.end_openram()
+```
 
 
 ## Command Line Usage (with library)
@@ -60,7 +78,6 @@ You can continue with following section for more details.
 
 
 ## Command Line Usage (without library)
-
 Once you have defined the environment, you can run OpenRAM from the command line
 using a single configuration file written in Python.