Added zsh completions

[fredricocalamari]

Added zsh completion files. This feature allows zsh users to easily reference all options for keepassxc by typing into the zsh console:
keepassxc-cli command --<tab key>
--option1 --Description of option1
--option2 --Description of option2
...

I have included install.txt which contains instructions for end users and Linux distribution package maintaners on where it should be installed to.

Screenshots

Testing strategy

Place all of the _keepassxc* files (exclude install.txt) in the following folder:
/usr/share/zsh/site-functions/

Set permissions:
chmod 644 /usr/share/zsh/site-functions/_keepassxc*

Add the following lines to the file "~/.zshrc":
autoload -Uz compinit
compinit

Restart the terminal
Type into console "keepassxc-cli<space key>" then hit <tab key> to see the commands for the program.
Type in "keepassxc-cli edit -" then hit <tab key> to see the option arguments for the command.
It is possible to string options together, for example you can continue completing after "keepassxc-cli edit --key-file <file> by typing "<space key>-" and hitting <tab key> again to see additional options. The first option (e.g. --key-file in this example) does not appear again in the new list that appears since it was already used.

Type of change

• ✅ New feature (change that adds functionality)
• ✅ Documentation (non-code change)

[droidmonkey]

Why do we need completions for keepassxc? If anything you should make them for keepassxc-cli

[fredricocalamari]

Why do we need completions for keepassxc? If anything you should make them for keepassxc-cli

You're right. I'll make completions for keepassxc-cli and resubmit.
I finished the completions, however I need to fix a small bug that made zsh unexpectedly complete the commands for keepassxc-cli when not invoking keepassxc-cli. For example, typing in "ls <space><tab key>" in zsh was invoking the _keepassxc-cli_ls function with compinit. Obviously, that's not ideal. I'll fix it shortly and resubmit for review.