[web] Improve check spelling settings

[dgdavid]

Problem

Thanks to @imobachgs's review at #462 (comment), I realize that something was not working as expected with the check spelling task introduced in #448

Basically, using the allowCompoundWords: true goes to let go some typos.

Solution

• Set allowCompoundWords settings to false
• Add a couple of interesting dictionaries
• Create and use a custom dictionary because our ignoredWords list is too long already
• Please the check by changing some words

[coveralls]

Coverage: 79.96%. Remained the same when pulling aa58ad2 on improve-cspell-config into aaa58ee on master.