Improve visual consistency of fonts across browsers

[cicirello]

Summary
A sans serif font stack is currently in use that overall works well across browsers, platforms, etc. In some cases. when the last fallback (sans-serif) is used by the browser, the font is a bit smaller than on most other platforms. Specifically, on Android in Chrome, as well as in GitHub's Android app. In Android's case, sans-serif will lead to Android's default sans serif font, which is currently Roboto. Roboto is a bit narrower than Verdana and other sans serif fonts.

Possible Solution
One possible solution is to do what is done for repository badges generated by Shields.io and other badge generators. The badges by Shields use the textLength property to set a consistent length for text elements, causing the browser to scale the length of text as necessary to that target length.