Function comparative

This function returns the comparative form of an adjective.

Uses irregular forms for common words (good -> better) and heuristic rules for regular adjectives:

• 1 syllable: add -er (fast -> faster)
• 1 syllable ending in CVC: double consonant (big -> bigger)
• 2 syllables ending in -y: change y to -ier (happy -> happier)
• 2 syllables ending in -e: add -r (large -> larger)
• 2 syllables ending in -le or -ow: add -er (simple -> simpler, narrow -> narrower)
• 3+ syllables: use "more" (beautiful -> more beautiful)