feat: Migrate Vim and Tmux plugins to dedicated managers

Migrated Vim plugins from Git submodules to vim-plug, and Tmux plugins
to TPM (Tmux Plugin Manager).

This change:
- Updates `install.sh` to automatically install vim-plug and TPM.
- Modifies `dotfiles/vimrc` to configure plugins via vim-plug.
- Modifies `dotfiles/tmux.conf` to configure plugins via TPM.
- Removes all Vim and Tmux submodule entries from `.gitmodules`.
- Deletes the old submodule directories from the repository.

This streamlines plugin management, making updates easier and reducing
the complexity of the main `install.sh` script.

.gitmodules

@@ -1,24 +1 @@
-[submodule "dotfiles/vim/pack/matir/opt/solarized8"]
-	path = dotfiles/vim/pack/matir/opt/solarized8
-	url = https://github.com/lifepillar/vim-solarized8.git
-	fetchRecurseSubmodules = true
-[submodule "dotfiles/vim/pack/matir/start/surround"]
-	path = dotfiles/vim/pack/matir/start/surround
-	url = https://github.com/tpope/vim-surround.git
-	fetchRecurseSubmodules = true
-[submodule "dotfiles/vim/pack/matir/start/editorconfig"]
-	path = dotfiles/vim/pack/matir/start/editorconfig
-	url = https://github.com/editorconfig/editorconfig-vim.git
-	fetchRecurseSubmodules = true
-[submodule "dotfiles/vim/pack/matir/start/fugitive"]
-	path = dotfiles/vim/pack/matir/start/fugitive
-	url = https://github.com/tpope/vim-fugitive
-	fetchRecurseSubmodules = true
-[submodule "dotfiles/vim/pack/matir/start/ctrlp"]
-	path = dotfiles/vim/pack/matir/start/ctrlp
-	url = https://github.com/ctrlpvim/ctrlp.vim.git
-	fetchRecurseSubmodules = true
-[submodule "dotfiles/tmux/tmux-logging"]
-	path = dotfiles/tmux/tmux-logging
-	url = https://github.com/tmux-plugins/tmux-logging.git
-	fetchRecurseSubmodules = true
+