Fix style being missed on patchDocument

There were scenarios in which patching a document would result in loss
of style for the template runs and, possibly, their right-adjacent run
as well (post-splitting). That was due to the run style elements not
being added to the newly created runs.

This commit addresses this issue by introducing a new, optional, flag
for the `patchDocument` function: `keepOriginalStyles`. It defaults to
`false` (current behavior) and, when `true`, ensures that there is no
loss of styling.

This should address https://github.com/dolanmiu/docx/issues/2293.

src/patcher/replacer.ts

@@ -20,6 +20,7 @@ export const replacer = (
     patchText: string,
     renderedParagraphs: readonly IRenderedParagraphNode[],
     context: IContext,
+    keepOriginalStyles: boolean = false,
 ): Element => {
     for (const renderedParagraph of renderedParagraphs) {
         const textJson = patch.children
@@ -47,9 +48,29 @@ export const replacer = (
 
                 const index = findRunElementIndexWithToken(paragraphElement, SPLIT_TOKEN);
 
-                const { left, right } = splitRunElement(paragraphElement.elements![index], SPLIT_TOKEN);
+                const runElementToBeReplaced = paragraphElement.elements![index];
+                const { left, right } = splitRunElement(runElementToBeReplaced, SPLIT_TOKEN);
+
+                let newRunElements = textJson;
+                let patchedRightElement = right;
+
+                if (keepOriginalStyles) {
+                    const runElementNonTextualElements =
+                        runElementToBeReplaced.elements?.filter((e) => e.type === "element" && e.name !== "w:t") ?? [];
+
+                    newRunElements = textJson.map((e) => ({
+                        ...e,
+                        elements: [...runElementNonTextualElements, ...(e.elements ?? [])],
+                    }));
+
+                    patchedRightElement = {
+                        ...right,
+                        elements: [...runElementNonTextualElements, ...(right.elements ?? [])],
+                    };
+                }
+
                 // eslint-disable-next-line functional/immutable-data
-                paragraphElement.elements!.splice(index, 1, left, ...textJson, right);
+                paragraphElement.elements!.splice(index, 1, left, ...newRunElements, patchedRightElement);
                 break;
             }
         }