Add windows compiling and installing guide in readme

[VeryEvilHumna]

I also ran into a type issue (trying to pass i32 in u32) while compiling on Windows. Compiler suggested a patch that fixed the problem, but I have no experience with Rust and no time to test if it breaks Linux build, that's why I haven't included it in the PR. There is the patch from git:

diff --git a/src/ocr.rs b/src/ocr.rs
index ef0e193..53b8741 100644
--- a/src/ocr.rs
+++ b/src/ocr.rs
@@ -40,7 +40,7 @@ impl Ocr {
                     &CString::new("/dev/null").unwrap(),
                 )
                 .unwrap();
-            set_log_level(leptonica_sys::L_SEVERITY_ERROR);
+            set_log_level(leptonica_sys::L_SEVERITY_ERROR.try_into().unwrap());
         }
         if let Some(binarization) = binarization {
             leptess
@@ -77,7 +77,7 @@ impl Ocr {
         let filename = CString::new(img.as_str()).expect("null in filename");
         let mut cpix = leptonica_plumbing::Pix::read_with_hint(
             &filename,
-            leptonica_sys::L_JPEG_CONTINUE_WITH_BAD_DATA,
+            leptonica_sys::L_JPEG_CONTINUE_WITH_BAD_DATA.try_into().unwrap(),
         )?;

         if let Some(scale) = self.scale {

Maybe that's just because of newer leptonica version than one ocrlocate used on date of its initial creation