Example text improvements for legal keyword search

[JonellaCulmer]

What we're after

In order to better clarify the use of symbols in our keyword search, we need to improve the example text under the filter to show how symbols can be used correctly. This ticket is to document that example text and mock-up the appearance for the front-end.

Related tickets:

• Create user guide for legal search #6480

Legal searches with keyword

• https://www.fec.gov/data/legal/search/murs/
• https://www.fec.gov/data/legal/search/admin_fines/
• https://www.fec.gov/data/legal/search/advisory-opinions/
• https://www.fec.gov/data/legal/search/adrs/

These legal searches are somewhat different, I'm not sure we want to make any changes here:

• https://www.fec.gov/data/legal/search/regulations/ (This uses the ecfr API)
• https://www.fec.gov/data/legal/search/statutes/ (This currently only searches the title of the statute)

Completion criteria

• Mock-ups are created with new example text and approved by stakeholders.
• Example text is added to front-end ticket for implementation