feat: add cds-lsp (#2926)

* feat: added @sap/cds-lsp

* fix(cds-lsp): update root dir pattern

* fix(cds-lsp): cleanup double configuraton of root_dir copied from csslsp example

lua/lspconfig/server_configurations/cds_lsp.lua

@@ -0,0 +1,33 @@
+local util = require 'lspconfig.util'
+
+local root_files = {
+  'package.json',
+  'db',
+  'srv',
+}
+
+return {
+  default_config = {
+    cmd = { 'cds-lsp', '--stdio' },
+    filetypes = { 'cds' },
+    -- init_options = { provideFormatter = true }, -- needed to enable formatting capabilities
+    root_dir = util.root_pattern(unpack(root_files)),
+    single_file_support = true,
+    settings = {
+      cds = { validate = true },
+    },
+  },
+  docs = {
+    description = [[
+
+https://cap.cloud.sap/docs/
+
+`cds-lsp` can be installed via `npm`:
+
+```sh
+npm i -g @sap/cds-lsp
+```
+
+]],
+  },
+}