Rectangle commands for large file editing

### Problem It is difficult to modify large files (more than 10k lines) efficiently, as we are limited in cursors, as showed in the following gif.  While i do understand the possible problem to have more than 10k active cursors at the same time, i still think it would be nice to be able to edit large file. ### Solution and request I think emacs has a interesting solution for file editing without using multiple cursors: the [rectangle commands](https://www.gnu.org/software/emacs/manual/html_node/emacs/Rectangles.html). Maybe using this "marking" solution could enable vscode to modify larger file. Thanks.