fix: remove the v prefix when pulling a release

[bschaatsbergen]

Problem

Since 0.6.0 jumppad stopped prefixing releases with a v, see: https://github.com/jumppad-labs/jumppad/releases

Which resulted in the error:

Installing Jumppad to /usr/local/bin/jumppad

Please note: You may be prompted for your password

To remove Jumppad and all configuration use the command "jumppad uninstall"

Downloading https://github.com/jumppad-labs/jumppad/releases/download/v0.9.1/jumppad_0.9.1_darwin_arm64.zip
Unzipping download
Archive:  jumppad.zip
  End-of-central-directory signature not found.  Either this file is not
  a zipfile, or it constitutes one disk of a multi-part archive.  In the
  latter case the central directory and zipfile comment will be found on
  the last disk(s) of this archive.
...

Fix

Simply remove the v from when pointing to the release URL.

Additional notes

• On the docs, installation through Brew was a bit farther down the page, so my simple brain turned to the install.sh.
  Would it be helpful to move the "Package managers" section a bit higher? I'll happily raise a follow-up PR.

• install.sh should raise the NotFound error, and not try to unzip something that isn't downloaded.

[nicholasjackson]

TY