Merge pull request #20601 from neovim/backport-20576-to-release-0.8

[Backport release-0.8] feat(man): add health check

runtime/lua/man/health.lua

@@ -0,0 +1,20 @@
+local M = {}
+
+local report_ok = vim.fn['health#report_ok']
+local report_error = vim.fn['health#report_error']
+
+local function check_runtime_file(name)
+  local path = vim.env.VIMRUNTIME .. '/' .. name
+  if vim.loop.fs_stat(path) then
+    report_error(string.format('%s detected. Please delete %s', name, path))
+  else
+    report_ok(string.format('%s not in $VIMRUNTIME', name))
+  end
+end
+
+function M.check()
+  check_runtime_file('plugin/man.vim')
+  check_runtime_file('autoload/man.vim')
+end
+
+return M