chore: fix some grammar errors in theme doc generation script (#4402)

Author: qwerty541

scripts/generate-theme-doc.js

@@ -22,15 +22,15 @@ Use \`?theme=THEME_NAME\` parameter like so:
 
 ## Stats
 
-> These themes works with all five our cards: Stats Card, Repo Card, Gist Card, Top languages Card and WakaTime Card.
+> These themes work with all five of our cards: Stats Card, Repo Card, Gist Card, Top Languages Card, and WakaTime Card.
 
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 ${STAT_CARD_TABLE_FLAG}
 
 ## Repo Card
 
-> These themes works with all five our cards: Stats Card, Repo Card, Gist Card, Top languages Card and WakaTime Card.
+> These themes work with all five of our cards: Stats Card, Repo Card, Gist Card, Top Languages Card, and WakaTime Card.
 
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 | :--: | :--: | :--: |