Merge pull request #205 from zpg6/docs/link-to-esp32-example

docs: adds esp32 example

Author: thejpster

README.md

@@ -80,6 +80,7 @@ This repository houses no examples for no-std usage, however you can check out t
 * [Pi Pico](https://github.com/rp-rs/rp-hal-boards/blob/main/boards/rp-pico/examples/pico_spi_sd_card.rs)
 * [STM32H7XX](https://github.com/stm32-rs/stm32h7xx-hal/blob/master/examples/sdmmc_fat.rs)
 * [atsamd(pygamer)](https://github.com/atsamd-rs/atsamd/blob/master/boards/pygamer/examples/sd_card.rs)
+* [ESP32 (esp-hal + Embassy)](https://github.com/zpg6/esp32-sdcard)
 
 ## Todo List (PRs welcome!)