feat: add plugin for linting

Author: fredrikaverpil

init.lua

@@ -585,6 +585,7 @@ require('lazy').setup {
       local ensure_installed = vim.tbl_keys(servers or {})
       vim.list_extend(ensure_installed, {
         'stylua', -- Used to format lua code
+        'markdownlint', -- Used to lint markdown
       })
       require('mason-tool-installer').setup { ensure_installed = ensure_installed }
 
@@ -623,6 +624,59 @@ require('lazy').setup {
     },
   },
 
+  { -- Linting
+    'mfussenegger/nvim-lint',
+    event = { 'BufReadPre', 'BufNewFile' },
+    config = function()
+      local lint = require 'lint'
+      lint.linters_by_ft = {
+        markdown = { 'markdownlint' },
+      }
+
+      -- To allow other plugins to add linters to require('lint').linters_by_ft,
+      -- instead set linters_by_ft like this:
+      -- lint.linters_by_ft = lint.linters_by_ft or {}
+      -- lint.linters_by_ft['markdown'] = { 'markdownlint' }
+      --
+      -- However, note that this will enable a set of default linters,
+      -- which will cause errors unless these tools are available:
+      -- {
+      --   clojure = { "clj-kondo" },
+      --   dockerfile = { "hadolint" },
+      --   inko = { "inko" },
+      --   janet = { "janet" },
+      --   json = { "jsonlint" },
+      --   markdown = { "vale" },
+      --   rst = { "vale" },
+      --   ruby = { "ruby" },
+      --   terraform = { "tflint" },
+      --   text = { "vale" }
+      -- }
+      --
+      -- You can disable the default linters by setting their filetypes to nil:
+      -- lint.linters_by_ft['clojure'] = nil
+      -- lint.linters_by_ft['dockerfile'] = nil
+      -- lint.linters_by_ft['inko'] = nil
+      -- lint.linters_by_ft['janet'] = nil
+      -- lint.linters_by_ft['json'] = nil
+      -- lint.linters_by_ft['markdown'] = nil
+      -- lint.linters_by_ft['rst'] = nil
+      -- lint.linters_by_ft['ruby'] = nil
+      -- lint.linters_by_ft['terraform'] = nil
+      -- lint.linters_by_ft['text'] = nil
+
+      -- Create autocommand which carries out the actual linting
+      -- on the specified events.
+      local lint_augroup = vim.api.nvim_create_augroup('lint', { clear = true })
+      vim.api.nvim_create_autocmd({ 'BufEnter', 'BufWritePost', 'InsertLeave' }, {
+        group = lint_augroup,
+        callback = function()
+          require('lint').try_lint()
+        end,
+      })
+    end,
+  },
+
   { -- Autocompletion
     'hrsh7th/nvim-cmp',
     event = 'InsertEnter',