Automatically reduce columns as the breakpoint gets smaller on Grid.

[alan-cole]

User story

As a tablet user
I want to see 3 columns on desktop becomes 2 columns on tablet
So that elements in the columns aren't too thin to read the content within.

Description

Provide an option to automatically include sensible col- classes when using template_column_count, particularly for column counts greater than 3.

Example implementation:

template_column_count = 6 columns

I get:
- 6 columns at 1440px (xxl) breakpoint
- 3 columns at 1280px (xl) breakpoint
- 2 columns at 768px (m) breakpoint
- 1 column at everything below

template_column_count = 4 columns

I get:
- 4 columns at 1440px (xxl) breakpoint
- 3 columns at 1280px (xl) breakpoint
- 2 columns at 768px (m) breakpoint
- 1 column at everything below

template_column_count = 3 columns

I get:
- 3 columns at 1280px (xl) breakpoint
- 2 columns at 768px (m) breakpoint
- 1 column at everything below

template_column_count = 2 columns

I get:
- 2 columns at 768px (m) breakpoint
- 1 column at everything below

Acceptance criteria

Given I am a
When I
Then I