[input] lowercase params.spellcheck

This ensures the behave is the same as the nunjucks templates when a
boolean value is passed.

Author: MatMoore

nhsuk_frontend_jinja/nhsuk/components/input/template.jinja

@@ -50,7 +50,7 @@
     <input class="nhsuk-input
     {%- if params.classes %} {{ params.classes }}{% endif %}
     {%- if params.errorMessage %} nhsuk-input--error{% endif %}" id="{{ id }}" name="{{ params.name }}" type="{{ params.type | default('text') }}"
-    {%- if params.spellcheck not in [none, undefined] %} spellcheck="{{ params.spellcheck }}"{% endif %}
+    {%- if params.spellcheck not in [none, undefined] %} spellcheck="{{ params.spellcheck | lower }}"{% endif %}
     {%- if params.value %} value="{{ params.value }}"{% endif %}
     {%- if describedBy %} aria-describedby="{{ describedBy }}"{% endif %}
     {%- if params.autocomplete %} autocomplete="{{ params.autocomplete }}"{% endif %}