feat(#2598): add api.tree.resize (#2811)

* feat(#2598): Implemented API `tree.resize`

* rely on  when resize

* Fix docs

---------

Co-authored-by: Alexander Courtis <alex@courtis.org>

lua/nvim-tree/actions/tree/resize.lua

@@ -0,0 +1,51 @@
+local view = require "nvim-tree.view"
+
+local M = {}
+
+---Resize the tree, persisting the new size.
+---@param opts ApiTreeResizeOpts|nil
+function M.fn(opts)
+  if opts == nil then
+    -- reset to config values
+    view.configure_width()
+    view.resize()
+    return
+  end
+
+  local options = opts or {}
+  local width_cfg = options.width
+
+  if width_cfg ~= nil then
+    view.configure_width(width_cfg)
+    view.resize()
+    return
+  end
+
+  if not view.is_width_determined() then
+    -- {absolute} and {relative} do nothing when {width} is a function.
+    return
+  end
+
+  local absolute = options.absolute
+  if type(absolute) == "number" then
+    view.resize(absolute)
+    return
+  end
+
+  local relative = options.relative
+  if type(relative) == "number" then
+    local relative_size = tostring(relative)
+    if relative > 0 then
+      relative_size = "+" .. relative_size
+    end
+
+    view.resize(relative_size)
+    return
+  end
+end
+
+function M.setup(opts)
+  M.config = opts or {}
+end
+
+return M