Sets the list of directories in which the `GtkSourceSnippetManager` looks for snippet files.
If dirs is null, the search path is reset to default.
At the moment this function can be called only before the snippet files are loaded for the first time. In practice to set a custom search path for a `GtkSourceSnippetManager`, you have to call this function right after creating it.
| this | |
| dirs |
a null-terminated array of strings or null. |