docs: add udf uast_children to the documentation

Signed-off-by: Manuel Carmona <[email protected]>

Author: mcarmonaa

docs/using-gitbase/functions.md

@@ -12,7 +12,8 @@ To make some common tasks easier for the user, there are some functions to inter
 |uast(blob, [lang, [xpath]])json_blob| returns an array of UAST nodes as blobs in semantic mode                                                 |
 |uast_mode(mode, blob, lang)json_blob| returns an array of UAST nodes as blobs specifying its language and mode (semantic, annotated or native) |
 |uast_xpath(json_blob, xpath)| performs an XPath query over the given UAST nodes                                                                |
-|uast_extract(json_blob, key)| extracts information identified by the given key from the uast nodes                                              |
+|uast_extract(json_blob, key)| extracts information identified by the given key from the uast nodes                                             |
+|uast_children(json_blob)| returns a flattened array of the children UAST nodes from each one of the UAST nodes in the given array              |
 
 ## Standard functions