Exclude generic HEAR/HER cards for DC (#192)

## Description

DC has rolled out their HEAR/HER rebates. This PR removes the "coming
soon" cards.
[Asana](https://app.asana.com/0/1207456219977120/1208649430166793/f)

This repo also doesn't appear to work with Node v20, and although we
specify 18 in the README, we don't enforce it. This PR adds an `.nvmrc`
to make that easier.

## Test Plan

check Weatherization category for a low income 20002 zip code household
to make sure that the "Expected in 2024-2025" cards don't show up
anymore

.nvmrc

@@ -0,0 +1 @@
+v18.19.1

src/ira-rebates.ts

@@ -59,8 +59,8 @@ const hearRebates: {
  * As states launch their HEAR and HER programs, we'll want to stop showing this
  * generic info to users in those states.
  */
-const HEAR_EXCLUDE_STATES = new Set(['ME', 'NY', 'RI']);
-const HER_EXCLUDE_STATES = new Set(['ME', 'WI']);
+const HEAR_EXCLUDE_STATES = new Set(['DC', 'ME', 'NY', 'RI']);
+const HER_EXCLUDE_STATES = new Set(['DC', 'ME', 'WI']);
 
 export function getRebatesFor(response: APIResponse, msg: MsgFn): IRARebate[] {
   const disclaimerText = msg(