feat: add harper_ls support (#3001)

* feat: added `harper_ls` support

* fix(unused parameter): removed settings parameter from `harper_ls` config

Co-authored-by: Raphael <glephunter@gmail.com>

---------

Co-authored-by: Raphael <glephunter@gmail.com>

lua/lspconfig/server_configurations/harper_ls.lua

@@ -0,0 +1,36 @@
+local util = require 'lspconfig.util'
+
+return {
+  default_config = {
+    cmd = { 'harper-ls', '--stdio' },
+    filetypes = {
+      'markdown',
+      'rust',
+      'typescript',
+      'typescriptreact',
+      'javascript',
+      'python',
+      'go',
+      'c',
+      'cpp',
+      'ruby',
+      'swift',
+      'csharp',
+      'toml',
+      'lua',
+    },
+    root_dir = util.find_git_ancestor,
+    single_file_support = true,
+  },
+  docs = {
+    description = [[
+https://github.com/chilipepperhott/harper_ls
+
+The language server for Harper, the slim, clean language checker for developers.
+As of right now, there are no settings to be configured for `harper_ls`.
+    ]],
+    default_config = {
+      root_dir = [[bufdir]],
+    },
+  },
+}