Edit README.md So That Library Nicknames Are Consistent to Facilitate Copying-and-Pasting

[cjsha]

This issue is attempting to facilitate copying-and-pasting of motifs from one schematic to another schematic (in particular, schematics that were made by different users).

For instance:
When symbols are placed on a schematic and assigned a footprint, the footprint is assigned with the following notation: <footprint-library-nickname>:<footprint-name>. Therefore, symbols that are copied from a document made by a user and pasted into a document made by another user generates DRC complaints ("The current configuration does not include the library `open-ephys") if those users set different nicknames for the Open Ephys libraries in the Library Manager. This creates an annoyance for users copying-and-pasting circuit motifs from documents that were created in an environment where the Open Ephys KiCad libraries have different nicknames.

@cjsha uses the nickname oe. @jonnew uses the nickname open-ephys. Let's settle on one and make it an "official" KiCad library nickname for developers of Open Ephys hardware by putting it in the README.md.