Add language to hearings page to refer people to SERS for archived hearings

[dorothyyeager]

User story
As a Commission website user or stakeholder, I want to access important rulemaking hearings of recent note, but also be able to reach archived ones.

What we're after
In #2394 we drafted language for the hearings tab to refer users to SERS for archived hearing pages and files. Because Because https://www.fec.gov/meetings/?tab=hearings is hard-coded, we will need a front-end person to implement that language and add link to SERS.

To do

• Add this sentence to the description at the top of https://www.fec.gov/meetings/?tab=hearings:

This page lists upcoming public hearings as well as those held from 2005 through the present. Use SERS to search for all archived rulemaking hearings.

• Add the link to SERS in that sentence so that it points to http://sers.fec.gov/fosers/