Move lsp config to local file structure

.config/nvim/lsp/herb_ls.lua

@@ -0,0 +1,29 @@
+---@brief
+---
+--- https://www.npmjs.com/package/@herb-tools/language-server
+--- https://github.com/marcoroth/herb
+---
+--- HTML+ERB (HTML + Embedded Ruby)
+--- Powerful and seamless HTML-aware ERB parsing and tooling.
+---
+--- Herb is designed from the ground up to deeply understand `.html.erb` files,
+--- preserving both HTML and embedded Ruby structure without losing any details.
+---
+--- `herb-language-server` can be installed via `npm`:
+---
+--- ```sh
+--- npm install -g @herb-tools/language-server
+--- ```
+---
+--- or via `yarn`:
+---
+--- ```sh
+--- yarn global add @herb-tools/language-server
+--- ```
+
+---@type vim.lsp.Config
+return {
+  cmd = { 'herb-language-server', '--stdio' },
+  filetypes = { 'html', 'eruby' },
+  root_markers = { 'Gemfile', '.git' },
+}