Browser ext: Handle table has <th> at start of each table row.

[LeeWannacott]

Sort gets messed up if each table row has <th> at the start. Ops/sec doesn't infer numeric-sort check if its because of this, or some other reason.

• http://vanilla-js.com/
• https://www.gov.uk/government/publications/local-stop-smoking-services-and-support-additional-funding/local-stop-smoking-services-and-support-funding-allocations-and-methodology#smoking-prevalence-and-confirmed-funding-allocations-by-local-authority

[LeeWannacott]

Fixed for the most part in https://github.com/LeeWannacott/table-sort-js/releases/tag/v1.20.0

numeric-sort needs to handle currency and vanilla js ops has spans with the value in them; which isn't sorted.

Tests for this need to be written, I only manually tested this. This will most likely require rejigging testing not just writing the tests...