Spelling: common words like "desktop" are recognised (#520) (#522)

The English speller only knew the 1990s Moby word list plus a small
hard-coded EXTRA array, so everyday modern words (desktop, laptop,
download, upload, spreadsheet, database, screenshot, inbox, offline,
workplace…) were flagged. Inflection, doubled-consonant and prefix rules
also only looked stems up in Moby, so even supplemented words failed in
inflected forms (blogging, uploader).

- New supplement assets/spelling/en-extra.txt: ~220 lowercase base forms,
  our own list (MIT OR Apache-2.0), replacing the EXTRA array.
- All stem lookups (inflections, doubled consonant, prefixes) consult the
  dictionary and the supplement; suggestions include supplement words.
- Regression tests: common modern words and inflections accepted,
  misspellings still flagged, "dekstop" suggests "desktop"; the list
  stays sorted and lowercase.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: Brandon Thomas <echelon@gmail.com>

assets/spelling/en-extra.txt

@@ -0,0 +1,224 @@
+# English spelling supplement: common words the public-domain Moby list (1990s) lacks.
+# Written by WordCraft contributors (MIT OR Apache-2.0); see ATTRIBUTION.md.
+# One lowercase base form per line, sorted. Plurals, -ed, -ing, -er, -ly… come from the
+# inflection rules in crates/proof/src/lib.rs, so list "desktop", not "desktops".
+airbag
+airfare
+artcraft
+autocomplete
+autocorrect
+autofill
+autoformat
+autosave
+backend
+bitcoin
+bitmap
+blockchain
+blog
+blogger
+bluetooth
+captcha
+caregiver
+carpool
+cellphone
+chatbot
+chatroom
+checkbox
+checklist
+childcare
+clickable
+configurable
+copyedit
+coronavirus
+covid
+crowdfunding
+crowdsource
+crypto
+cryptocurrency
+customizable
+customization
+cyber
+cybersecurity
+cyberspace
+database
+dataset
+daycare
+desktop
+download
+downloadable
+downsize
+dropdown
+earbud
+ebook
+ecommerce
+email
+emoji
+emoticon
+esports
+facebook
+favicon
+fintech
+firewall
+flowchart
+foodie
+freeware
+frontend
+fundraiser
+gameplay
+gamification
+geeky
+geolocation
+gigabit
+gigabyte
+github
+globalization
+google
+groupthink
+hackathon
+hardcode
+hashtag
+healthcare
+homepage
+homeschool
+hotspot
+hyperlink
+hypertext
+inbox
+incentivize
+infographic
+instagram
+internet
+interoperability
+intranet
+ipad
+iphone
+javascript
+kickstart
+kilobyte
+laptop
+lifestyle
+linkedin
+linux
+livestream
+lockdown
+login
+logout
+lowercase
+makeover
+malware
+megabyte
+megapixel
+meme
+metadata
+microchip
+microsoft
+middleware
+mindset
+multicultural
+multiplayer
+multitask
+nerdy
+netbook
+netflix
+newsfeed
+offboard
+offline
+onboard
+online
+onscreen
+outsource
+paralegal
+passcode
+petabyte
+phishing
+photobomb
+playdate
+playlist
+plugin
+podcast
+popup
+prequel
+printout
+prioritization
+prioritize
+ransomware
+recyclable
+ringtone
+roadmap
+rollout
+runtime
+scalability
+screencast
+screensaver
+screenshot
+scrollbar
+selfie
+signup
+sitemap
+skillset
+smartphone
+smartwatch
+smiley
+snowboard
+spellcheck
+spellchecker
+spreadsheet
+spyware
+stakeholder
+standup
+startup
+subfolder
+sunscreen
+superfood
+superuser
+tagline
+takeout
+techie
+telecommute
+teleconference
+telehealth
+telemedicine
+terabyte
+textbox
+timeline
+timestamp
+toolbar
+toolkit
+touchpad
+touchscreen
+trackball
+trackpad
+upcycle
+upload
+uppercase
+upsell
+upskill
+usability
+username
+videoconference
+videogame
+vlog
+vlogger
+voicemail
+walkthrough
+webcam
+webcast
+webinar
+weblog
+webmaster
+webpage
+website
+whatsapp
+whiteboard
+wifi
+wiki
+wikipedia
+wireframe
+wordcraft
+workaround
+workflow
+workforce
+workplace
+workspace
+workstation
+youtube