The CI badge in mathlib's README links to the svg

Stream: mathlib4

[Geoffrey Irving]

If I click on the green CI badge at the top of the mathlib4 readme on Github, I'm taken to a page containing the badge svg itself, rather than actual build runs:

https://github.com/leanprover-community/mathlib4/workflows/continuous%20integration/badge.svg?branch=master

This is because the syntax is just

![GitHub CI](https://github.com/leanprover-community/mathlib4/workflows/continuous%20integration/badge.svg?branch=master)

In contrast, if you ask Github to generate a badge you get something like

[![build](https://github.com/girving/ray/actions/workflows/lean.yml/badge.svg)](https://github.com/girving/ray/actions/workflows/lean.yml)

which links to a nice page of build results. Unfortunately I'm not sure how to fix this, since I can't find where the exact analogue build page is; maybe it doesn't exist due to bors?

[Bryan Gin-ge Chen]

Probably this page would be most useful to link to, since it shows the build results that run right before bors merges commits into master: https://github.com/leanprover-community/mathlib4/actions/workflows/bors.yml