plugin: install, configure Grammalecte

- Grammalecte is a French language checker. This plugin requires the
  python package `Grammalecte` that provide `grammalecte-cli` and
  `grammalecte-server`.

Co-Authored-by: iGor milhit <igor@milhit.ch>

lua/custom/plugins/grammalecte.lua

@@ -0,0 +1,14 @@
+-- Plugin to get Grammalecte checks in (neo)vim.
+
+-- Set the path to the grammalecte-cli executable
+vim.cmd([[ let g:grammalecte_cli_py = "/usr/bin/grammalecte-cli" ]])
+
+return {
+  "dpelle/vim-Grammalecte",
+  ft = {
+    "pandoc",
+    "markdown",
+    "text",
+    "gitcommit"
+  }
+}