fix(ci): bump luarocks-tag release version + enable PR test runs

[mrcjkb]

There was a bug in the luarocks-tag-release workflow, preventing the plugin and autoload directories from being added to the luarocks package.

The latest version of the workflow fixes it, so I've bumped it here.
I've also added pull_request as a trigger, so it can run (without uploading to luarocks) on PRs.

This time, I've manually tested it in Neovim with the following minimal config:

-- minimal.lua
-- Copy this to an empty test directory and start with
-- luarocks install --tree $(realpath .) quick-scope
-- nvim -u minimal.lua test.txt

-- Ignore default config
local config_path = vim.fn.stdpath('config')
vim.opt.rtp:remove(config_path)

-- Ignore default plugins
local data_path = vim.fn.stdpath('data')
local pack_path = data_path .. '/site'
vim.opt.packpath:remove(pack_path)

vim.opt.runtimepath:append('lib/luarocks/rocks-5.1/quick-scope/scm-1/')

...and it works 🎉