feat(terminal-integration): add `toggleterm-manager.nvim`

[LumenYoung]

📑 Description

Create a config for the toggleterm manager plugin, which uses telescope to give you clear overview on the toggleterm buffers you opened.

ℹ Additional Information

I've added addtional keymaps in the telescope interface to make it easy to use. Also I mapped <Leader>ts to this plugin.

[github-actions[bot]]

Review Checklist

Does this PR follow the [Contribution Guidelines](development guidelines)? Following is a partial checklist:

Proper conventional commit scoping:

• If you are adding a new plugin, the scope would be the name of the category it is being added into. ex. feat(utility): added noice.nvim plugin

• If you are modifying a pre-existing plugin or pack, the scope would be the name of the plugin folder. ex. fix(noice-nvim): fix LSP handler error

• [x] Pull request title has the appropriate conventional commit type and scope where the scope is the name of the pre-existing directory in the project as described above

• [x] README is properly formatted and uses fenced in links with <url> unless they are inside a [title](url)

• [x] Proper usage of opts table rather than setting things up with the config function.

[LumenYoung]

Thanks!