change todos counter position & format ( for large counts )

app/assets/javascripts/header.js

app/assets/javascripts/lib/utils/text_utility.js

app/assets/stylesheets/pages/todos.scss

app/controllers/dashboard/todos_controller.rb

app/helpers/todos_helper.rb

app/views/layouts/header/_default.html.haml

changelogs/unreleased/26703-todos-count.yml

doc/workflow/todos.md

spec/features/todos/todos_spec.rb

spec/javascripts/header_spec.js

spec/javascripts/lib/utils/text_utility_spec.js.es6