Get the real language for src blocks from the org source.

src/intermediate/src_block.rs

@@ -5,6 +5,7 @@ use crate::error::CustomError;
 #[derive(Debug, Clone)]
 pub(crate) struct ISrcBlock {
     pub(crate) lines: Vec<String>,
+    pub(crate) language: Option<String>,
 }
 
 intermediate!(
@@ -18,6 +19,7 @@ intermediate!(
             .split_inclusive('\n')
             .map(|s| s.to_owned())
             .collect();
-        Ok(ISrcBlock { lines })
+        let language = original.language.map(str::to_owned);
+        Ok(ISrcBlock { lines, language })
     }
 );