Point out issue with failing builds due to syntax errors

This is a trap "for young players" an loosing feedback from rustc or
your favorite code analysis tools won't make things better. Let's point
out the issue and the solution given in issue mozilla#472 upfront.

docs.md

@@ -68,6 +68,23 @@ fn main() {
 
 You can add configuration options using the [`Builder`](https://docs.rs/cbindgen/*/cbindgen/struct.Builder.html#methods) interface.
 
+When actively working on code, you likely don't want cbindgen to fail the entire build. Instead of expect-ing the result of the header generation, you could [ignore parse errors](https://github.com/mozilla/cbindgen/issues/472#issuecomment-831439826) and let rustc or your code analysis bring up:
+
+```rust
+    // ...
+    .generate()
+    .map_or_else(
+        |error| match error {
+            cbindgen::Error::ParseSyntaxError { .. } => {}
+            e => panic!("{:?}", e),
+        },
+        |bindings| {
+            bindings.write_to_file("target/include/edrs.h");
+        },
+    );
+}
+```
+
 Be sure to add the following section to your Cargo.toml:
 
 ```