Remove unused debug code in Compress/Zstd*.cpp

Update to 7-Zip Version 21.03

Update version numbers

Update to 7-Zip Version 21.02

Update README.md

change hot-key ALT+UP, add CTRL+RIGHT/LEFT

Windows Explorer and TotalCommander use ALT+UP as a hotkey to return to the upper level of the directory, but 7-ZIP defines it as synchronizing the path of the current panel to another panel, which often leads to incorrect operations.
Now change it to the same behavior mode as the above application, and add hotkeys CTRL+LEFT and CTRL+RIGHT to provide the function of synchronizing the panel path, which is similar but not exactly the same as TotalCommander.

Update zstd to version 1.4.8

Update README.md

Update version numbers

Update README.md for new brotli version