Here this section could help you ..
https://experienceleague.adobe.com/docs/experience-manager-65/administering/operations/configure-ric...
1. You can download a new Dictionary which allows Caps letter and use that instead of OOTB
2. OOTB dictionary at path /libs/cq/spellchecker/dictionaries(/libs/cq/spellchecker/dictionaries/en_us.dic) does not have Caps letters.
you can overlay this path with dictionary and try adding Caps letters there. it can work or go with new dictionary.
I mean its all mentioned in documentation just give it a read.