Add NeoVim test runner

For the queries that can't be tested with `tree-sitter` itself.

scripts/dummy_plugin/queries/bp

@@ -0,0 +1 @@
+../../../queries

scripts/minimal_init.lua

@@ -0,0 +1,40 @@
+vim.opt.runtimepath:append(vim.env.NVIM_PLENARY)
+vim.opt.runtimepath:append(vim.env.NVIM_TREESITTER)
+vim.opt.runtimepath:append(vim.env.NVIM_TREESITTER_TEXTOBJECTS)
+vim.opt.runtimepath:append(vim.env.NVIM_TREESITTER_PARSER)
+
+vim.cmd.runtime({ "plugin/plenary.vim", bang = true })
+vim.cmd.runtime({ "plugin/nvim-treesitter.lua", bang = true })
+vim.cmd.runtime({ "plugin/nvim-treesitter-textobjects.lua", bang = true })
+
+local Path = require("plenary.path")
+
+local project_root =  Path:new(".") -- FIXME: relies on current working directory
+
+vim.filetype.add({
+  extension = {
+    bp = "bp",
+  },
+})
+
+vim.o.swapfile = false
+vim.bo.swapfile = false
+
+local parser_config = require("nvim-treesitter.parsers").get_parser_configs()
+parser_config.bp = {
+  install_info = {
+    url = project_root.filename,
+    files = {"src/parser.c"},
+  },
+}
+
+require("nvim-treesitter.configs").setup({
+  indent = { enable = true },
+  highlight = { enable = true },
+})
+
+-- We need a hierarchy of `queries/bp/*.scm` in the runtimepath, otherwise
+-- `nvim-treesitter` doesn't enable some of its features (e.g: folding).
+-- The dummy plugin has a symlink following that format for our queries.
+local dummy_plugin_path = project_root / "scripts" / "dummy_plugin"
+vim.opt.runtimepath:append(dummy_plugin_path.filename)