Addition of a "read more" button in "Why It Matters" text

[richiecroker]

Some of our Why It Matters text is getting longer, as we are trialling putting in all of NHS England guidance into the section. THis may lead to formatting issues on the site, and so @evansd and I have discussed using Javascript to allow the text to be truncated with a "read more" hyperlink or button instead (something possibly like this.