fix nullref if close combobox with null item, #build

#build

fix release notes url link for 2021 and later (fixes #31), #build

add explore theme folder button, #build

update readme, #build

set missing folder color red, rename MyConverter, add project exists …

…property value and converter, browse parent folder(s) if cannot Explore missing folder, #build

use streamreader for editor.log file (to fix "file is used by another…

… process"), #build

add Kill Process context menu for selected project and shortcut (Alt+…

…Q) , #build

add option to disable project folder rename, fix nullref if try to re…

…name after added project, disable grid navigation keys during cell edit, validate project rename better and restore old value if failed, #build

fix nullref error for GetUnityExePath, fix Add Project folder checkin…

…g, #build