Refactor neovim config (#2)

Changes include:

- [x] Use init.lua instead of init.vim
   - Some keybindings are still to be converted
- [x] Use packer as a package manager instead of vim-plug
- [ ] Use built-in lsp instead of coc.nvim
   - [x] Set up language servers
   - [x] Completion
   - [x] Formatting (previously coc-prettier, now neoformat)
   - [ ] Snippets
- [ ] Replace fzf with telescope.nvim
- [x] Implement treesitter syntax highlighting
   - More info: https://github.com/nvim-treesitter/nvim-treesitter

Note that this requires neovim nightly until 0.5 is released

Reviewed-on: #2
Co-authored-by: Marko Korhonen <marko@korhonen.cc>
Co-committed-by: Marko Korhonen <marko@korhonen.cc>

home/.config/nvim/lua/pluginmanager.lua

@@ -0,0 +1,90 @@
+local fn = vim.fn
+local cmd = vim.cmd
+
+-- Install packer if it's not yet installed
+local install_path = fn.stdpath('data') .. '/site/pack/packer/opt/packer.nvim'
+local packer_not_installed = fn.empty(fn.glob(install_path))
+
+if packer_not_installed > 0 then
+    print('Packer is not installed, cloning it now...')
+    cmd('silent !git clone https://github.com/wbthomason/packer.nvim ' ..
+            install_path)
+end
+
+-- Configure packer
+cmd 'packadd packer.nvim'
+local use = require('packer').use
+require('packer').startup(function()
+
+    -- The plugin manager itself
+    use {'wbthomason/packer.nvim', opt = true}
+
+    -- Colorscheme
+    use 'monsonjeremy/onedark.nvim'
+
+    -- Statusline
+    use {
+        'hoob3rt/lualine.nvim',
+        requires = {'kyazdani42/nvim-web-devicons', opt = true}
+    }
+
+    -- Tabline/bufferline
+    use {
+        'akinsho/nvim-bufferline.lua',
+        requires = 'kyazdani42/nvim-web-devicons'
+    }
+
+    -- Indent characters
+    --use "lukas-reineke/indent-blankline.nvim"
+
+    -- Tree explorer
+    use {'kyazdani42/nvim-tree.lua', requires = 'kyazdani42/nvim-web-devicons'}
+
+    -- Telescope
+    use {
+        'nvim-telescope/telescope.nvim',
+        requires = {{'nvim-lua/popup.nvim'}, {'nvim-lua/plenary.nvim'}}
+    }
+
+    -- Do stuff as sudo
+    use 'lambdalisue/suda.vim'
+
+    -- Read editorconfig settings
+    use 'editorconfig/editorconfig-vim'
+
+    -- Configs for built-in LSP
+    use 'neovim/nvim-lspconfig'
+
+    -- Install LSP executables
+    use 'kabouzeid/nvim-lspinstall'
+
+    -- Extensions for eclipse.jdt.ls
+    use 'mfussenegger/nvim-jdtls'
+
+    -- Completion framework
+    use 'nvim-lua/completion-nvim'
+
+    -- treesitter syntax highlight
+    use {
+        'nvim-treesitter/nvim-treesitter',
+        branch = '0.5-compat',
+        run = ':TSUpdate'
+    }
+
+    -- Syntax highlighting for languages
+    -- that are not supported by treesitter
+    use 'sheerun/vim-polyglot'
+
+    -- Formatter plugin
+    use 'sbdchd/neoformat'
+
+    -- Make editing passwords safer
+    use {
+        'https://git.zx2c4.com/password-store',
+        rtp = 'contrib/vim/redact_pass.vim'
+    }
+
+end)
+
+-- Install plugins if packer was not installed
+if packer_not_installed > 0 then cmd 'PackerInstall' end