ci: Runs spellcheck in merge queue. (matter-labs#574)

## What ❔

Runs spellcheck in merge queue.
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## Why ❔

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are the principles behind them? -->
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## Checklist

<!-- Check your PR fulfills the following items. -->
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- [x] PR title corresponds to the body of PR (we generate changelog
entries from PRs).
- [ ] Tests for the changes have been added / updated.
- [ ] Documentation comments have been added / updated.
- [x] Code has been formatted via `zk fmt` and `zk lint`.
- [ ] Spellcheck has been run via `cargo spellcheck
--cfg=./spellcheck/era.cfg --code 1`.

.github/workflows/check-spelling.yml

@@ -5,8 +5,9 @@ on:
     branches:
       - main
   pull_request:
+  merge_group:
 
-env: 
+env:
   CARGO_TERM_COLOR: always
 
 jobs:
@@ -17,7 +18,7 @@ jobs:
         uses: taiki-e/install-action@v2
         with:
           tool: cargo-spellcheck
-          
+
       - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
 
       - name: Run cargo-spellcheck