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/pluginconf/telescope.lua

@@ -0,0 +1,36 @@
+require('telescope').setup {
+    defaults = {
+        vimgrep_arguments = {
+            'rg', '--hidden', '--color=never', '--no-heading',
+            '--with-filename', '--line-number', '--column', '--smart-case'
+        },
+        prompt_prefix = "> ",
+        selection_caret = "> ",
+        entry_prefix = "  ",
+        initial_mode = "insert",
+        selection_strategy = "reset",
+        sorting_strategy = "descending",
+        layout_strategy = "horizontal",
+        layout_config = {
+            horizontal = {mirror = false},
+            vertical = {mirror = false}
+        },
+        file_sorter = require'telescope.sorters'.get_fuzzy_file,
+        file_ignore_patterns = {},
+        generic_sorter = require'telescope.sorters'.get_generic_fuzzy_sorter,
+        winblend = 0,
+        border = {},
+        borderchars = {'─', '│', '─', '│', '╭', '╮', '╯', '╰'},
+        color_devicons = true,
+        use_less = true,
+        path_display = {},
+        set_env = {['COLORTERM'] = 'truecolor'}, -- default = nil,
+        file_previewer = require'telescope.previewers'.vim_buffer_cat.new,
+        grep_previewer = require'telescope.previewers'.vim_buffer_vimgrep.new,
+        qflist_previewer = require'telescope.previewers'.vim_buffer_qflist.new,
+
+        -- Developer configurations: Not meant for general override
+        buffer_previewer_maker = require'telescope.previewers'.buffer_previewer_maker
+    },
+    pickers = {find_files = {find_command = {"fd", "-Ht", "f"}}}
+}