check to ensure some files do or do not exist

[hyperupcall]

for example, ~/.zhistory shouldn't exist (it should be at ~/.local/share/zhistory). would be more useful with files like ~/.vscode, gitlibs, krew, vagrant, etc. to ensure we do not pollute anything if configuration somehow fails

also check to ensure some directories exist, such as some under $XDG_CONFIG_HOME/$application, because those may need to exist beforehand before the application uses it (even if the respective environmental variable the application uses is set properly)