getting rid of tabs, adding nullls for sql, and adding telescope preview back in

after/plugin/null-ls.lua

@@ -1,6 +1,12 @@
 local null_ls = require("null-ls")
 
 null_ls.setup({
-    sources = {
-    },
+  sources = {
+    -- sql lint
+    null_ls.builtins.diagnostics.sqlfluff.with({
+      extra_args = { "--dialect", "postgres" },   -- change to your dialect
+    }),
+    -- postgres format
+    null_ls.builtins.formatting.pg_format
+  },
 })