Add Overleaf (#523)

* Add overleaf SVG

* Add Overleaf to README

* Add overleaf reference svg

* Cite CoreUI for Overleaf

* Add reference comparison

* Create overleaf.xml

* Fix overleaf Android vector

* Linebreaks for readability.

Co-authored-by: Terence Eden <edent@users.noreply.github.com>

images/reference/index.md

@@ -267,3 +267,4 @@ Where possible this links to the organisation's brand guidelines page.
 | <img src="/images/svg/etsy.svg" width="256" /> | <img src="/images/reference/etsy.png" width="256" /> | https://www.etsy.com/uk/press?ref=ftr |
 | <img src="/images/svg/foobar2000.svg" width="256" /> | <img src="/images/reference/foobar2000.jpg" width="256" /> | https://www.foobar2000.org/ |
 | <img src="/images/svg/intercom.svg" width="256" /> | <img src="/images/reference/intercom.svg" width="256" /> | https://www.intercom.com/press |
+| <img src="/images/svg/overleaf.svg" width="256" /> | <img src="/images/reference/overleaf.svg" width="256" /> | https://www.overleaf.com/for/partners/logos |

images/reference/overleaf.svg

@@ -0,0 +1 @@
+<svg id="Layer_1" data-name="Layer 1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" viewBox="0 0 841.89 852.62"><defs><mask id="mask" x="174.51" y="91.03" width="1280.35" height="670.56" maskUnits="userSpaceOnUse"><g id="b"><path id="a" d="M1454.86,761.33H174.77V91H1454.86Z" fill="#fff"/></g></mask></defs><title>stickers alt</title><g mask="url(#mask)"><path d="M753,112C662.45,76.7,334.23,63.65,333.68,259.49,237.92,320.8,174.51,420.79,174.51,527.67c0,129.22,104.74,233.91,234,233.91s234-104.74,234-233.91A233.93,233.93,0,0,0,491.82,309c-16.94-6.55-53.74-18.1-83.13-15.62-41.93,26.66-93.06,81.47-117.24,136.06,35.94-43.13,92.12-62,141.88-53.91A154.17,154.17,0,0,1,562.54,527.63c0,85.15-69.31,154.12-154.46,154.12a153.66,153.66,0,0,1-117.24-54c-41.5-48.86-52.2-101.83-43.64-153.6C276.77,292.65,492,189.4,652,149.74c-52.2,27.64-146.33,73-212.22,122.5C631.9,346.43,663,184.44,753,112Z" fill="#47a141"/></g></svg>