docs: added link cable reference

README.md

@@ -12,7 +12,7 @@ A Game Boy emulator that is written in Rust 🦀.
 * Simple navigable source-code
 * Web and SDL front-ends
 * Audio, with a pretty accurate APU
-* Serial Data Transfer (Link Cable) support
+* Serial Data Transfer ([Link Cable](https://en.wikipedia.org/wiki/Game_Link_Cable)) support
 * Game Boy Printer emulation
 * Support for multiple MBCs: MBC1, MBC2, MBC3, and MBC5
 * Variable CPU clock speed