feat: first version of locals

Locals will be the main interface to treesitter, through some functions:
    get_definitions(bufnr) : returns all the definitions in bufnr
    get_scopes(bufnr): returns all definitions in bufnr
    get_references(bufnr): returns all references in bufnr

lua/nvim-treesitter/locals.lua

@@ -0,0 +1,82 @@
+-- Functions to handle locals
+-- Locals are a generalization of definition and scopes
+-- its the way nvim-treesitter uses to "understand" the code
+local api = vim.api
+local ts = vim.treesitter
+local queries = require'nvim-treesitter.query'
+local parsers = require'nvim-treesitter.parsers'
+
+local M = {
+  locals={}
+}
+
+function M.collect_locals(bufnr)
+  local ft = api.nvim_buf_get_option(bufnr, "ft")
+  local query = queries.get_query(ft, "locals")
+
+  if ft then
+    local query = queries.get_query(ft, 'locals')
+    local parser = parsers.get_parser(bufnr)
+
+    if parser then
+      local root = parser:parse():root()
+      local start_row, _, end_row, _ = root:range()
+
+      local locals = {}
+
+      for prepared_match in queries.iter_prepared_matches(query, root, bufnr, start_row, end_row) do
+        table.insert(locals, prepared_match)
+      end
+
+      return locals
+    end
+  end
+end
+
+function M.on_lines(_, buf, _, firstline, lastline, new_lastline, _)
+  M.locals[buf] = M.collect_locals(buf)
+end
+
+function M.get_definitions(bufnr)
+  local locals = M.locals[bufnr]
+
+  local defs = {}
+
+  for _, loc in ipairs(locals) do
+    if loc.definition then
+      table.insert(defs, {definition=loc.definition, kind=loc.kind})
+    end
+  end
+
+  return defs
+end
+
+function M.get_scopes(bufnr)
+  local locals = M.locals[bufnr]
+
+  local scopes = {}
+
+  for _, loc in ipairs(locals) do
+    if loc.scope then
+      table.insert(scopes, loc.scope)
+    end
+  end
+
+  return scopes
+end
+
+function M.get_references(bufnr)
+  local locals = M.locals[bufnr or api.nvim_get_current_buf()]
+
+  local refs = {}
+
+  for _, loc in ipairs(locals) do
+    if loc.reference then
+      table.insert(refs, loc.reference)
+    end
+  end
+
+  return refs
+end
+
+return M