pub fn add_inner(&mut self, origin: ContentOrigin, mut chunks: Vec<CheckableChunk>) {
        self.index
            .entry(origin)
            .and_modify(|acc: &mut Vec<CheckableChunk>| {
                acc.append(&mut chunks);
            })
            .or_insert_with(|| chunks);
        // Ok(()) TODO make this failable
    }
Adds a set of `CheckableChunk`s to the documentation to be checked.
doc-chunks/src/lib.rs