add serde for Keyword (#465)

Co-authored-by: guillaume-be <[email protected]>

src/pipelines/keywords_extraction/pipeline.rs

@@ -31,12 +31,13 @@ use crate::pipelines::sentence_embeddings::{
 use crate::{Config, RustBertError};
 use regex::Regex;
 use rust_tokenizers::Offset;
+use serde::{Deserialize, Serialize};
 use std::borrow::Cow;
 use std::cmp::min;
 use std::collections::{HashMap, HashSet};
 
 /// # Keyword generated by a `KeywordExtractionModel`
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct Keyword {
     /// String representation of the keyword
     pub text: String,