Add ESP32 (#14)

Author: bugadani

README.md

@@ -20,7 +20,7 @@ $ target-gen elf target/riscv32imc-unknown-none-elf/release/esp-flashloader outp
 
 | name    | supported |
 | ------- | --------- |
-| esp32   | N         |
+| esp32   | Y         |
 | esp32s2 | Y         |
 | esp32s3 | Y         |
 | esp32c2 | Y         |

build.rs

@@ -8,6 +8,8 @@ fn main() {
     fs::copy("ld/loader.x", out_dir.join("loader.x")).unwrap();
     println!("cargo:rerun-if-changed=ld/loader.x");
 
+    #[cfg(feature = "esp32")]
+    let chip = "esp32";
     #[cfg(feature = "esp32s2")]
     let chip = "esp32s2";
     #[cfg(feature = "esp32s3")]