Add (some) support to terminal lists

[saucoide]

This is what i've been using since i had to stop using harpoon 1, decided to
clean it up a bit and submit it in case it is helpful for anyone else even if
it doesnt get merged

Summary of what it does:

• Adds a HarpoonTermList as a specialized list type for managing terminal buffers
• toggle_quick_menu works, deleting a terminal from there will kill the buffer too
• You can send commands with :send_command and also a selection or the current line with :send_selection

Adding __is_harpoon_list is pretty ugly but I dont know how to better tell
apart from a table with config to be merged and table with a full instance of
list

Usage would be something like This

local harpoon = require('harpoon')

harpoon.setup({ 
    settings = {
        save_on_toggle = true,
    },
    ["terms"] = require("harpoon.terms"):new()
})

-- Buffers
vim.keymap.set( "n", "<leader>a", function() harpoon:list():add() end, { desc = "Harpoon: Add file" })
vim.keymap.set( "n", "<leader>hh", function() harpoon.ui:toggle_quick_menu(harpoon:list()) end, { desc = "Harpoon: Toggle quick menu" })
vim.keymap.set( "n", "<leader>1", function() harpoon:list():select(1) end, { desc = "Harpoon: Go to file 1" })
vim.keymap.set( "n", "<leader>2", function() harpoon:list():select(2) end, { desc = "Harpoon: Go to file 2" })
vim.keymap.set( "n", "<leader>3", function() harpoon:list():select(3) end, { desc = "Harpoon: Go to file 3" })
vim.keymap.set( "n", "<leader>4", function() harpoon:list():select(4) end, { desc = "Harpoon: Go to file 4" })
vim.keymap.set( "n", "<leader>5", function() harpoon:list():select(5) end, { desc = "Harpoon: Go to file 5" })

-- Terminals
vim.keymap.set("n", "<leader>tt", function() harpoon.ui:toggle_quick_menu(harpoon:list("terms")) end, { desc = "Show harpoon terminal menu" })
-- nagivation
vim.keymap.set("n", "<leader>t1", function() harpoon:list("terms"):select(1) end, { desc = "Harpoon: Go to Terminal 1" })
vim.keymap.set("n", "<leader>t2", function() harpoon:list("terms"):select(2) end, { desc = "Harpoon: Go to Terminal 2" })
-- send specific commands
vim.keymap.set("n", "<C-l>1", function() harpoon:list("terms"):send_command(1, "clear") end, { desc = "Harpoon: Clear Terminal 1" })
vim.keymap.set("n", "<C-l>2", function() harpoon:list("terms"):send_command(2, "clear") end, { desc = "Harpoon: Clear Terminal 2" })
-- send selections
vim.keymap.set({"n", "v"}, "<C-CR>1", function() harpoon:list("terms"):send_selection(1, true) end, { desc = "Harpoon: Current selection to Terminal 1" })
vim.keymap.set({"n", "v"}, "<C-CR>2", function() harpoon:list("terms"):send_selection(2, true) end, { desc = "Harpoon: Current selection to Terminal 2" })