Add missing code sample readmes

[mDuo13]

Our contributor guidelines suggest that every code sample should have one top-level README.md file explaining the sample itself (which is used by the Code Samples page for the description of the code sample card), and another README.md file in each language subdirectory with instructions on how to install dependencies and run that code sample in that language. However, many code samples are missing these, something like 97 instances at the moment.

Run the following Python code from the top of the repo to get an updated list of directories that are missing a README:

import os
for dirpath, dirnames, filenames in os.walk("./_code-samples/"):
     pathlist = dirpath.split(os.path.sep)
     if len(pathlist) < 3 or len(pathlist) > 4:
         continue
     if set(pathlist) & {"node_modules", ".venv", "venv", "__pycache__"}:
         continue
     if "README.md" not in filenames:
         print(dirpath[16:])

[mDuo13]

As of #3493 this is done for JS and Python so it's only the Go and other miscellaneous code samples that don't have it at this point.