Custom CSS and JS on Django Admin

admin.py

# https://riptutorial.com/django/example/5359/additional-css-styles-and-js-scripts-for-admin-page
@admin.register(Person)
class PersonAdmin(admin.ModelAdmin):
    list_display = ('__str__',)
    date_hierarchy = 'created'
    search_fields = ('first_name', 'last_name', 'email')
    list_filter = (
        # 'uf',
        ('created', DateRangeFilter),
    )
    form = PersonForm

    class Media:
        css = {
            'all': ('css/admin/style.css',)
        }
        js = ('js/admin/main.js',)

main.js

$(function () {
   $('#searchbar').attr('placeholder', 'Search by name')
})

style.css

.field-first_name {
  background-color: #e6f2ff;
}

Thanks!