Use consistent title case for theme names

[jmooring]

Some of the names with two or more words use title case, while others use sentence case. It would be nice if these were consistent. I vote for title case as described in the Associated Press Stylebook.

This is mostly a cosmetic issue.

We're doing a strings.EqualFold comparison when doing the reverse lookup from theme name to d2themes.Theme.ID, so it's not causing any problems.

Current Name	Desired Name	Status
Aubergine	Aubergine	✔️
Buttered toast	Buttered Toast	❌
Colorblind clear	Colorblind Clear	❌
Cool classics	Cool Classics	❌
Earth tones	Earth Tones	❌
Everglade green	Everglade Green	❌
Flagship Terrastruct	Flagship Terrastruct	✔️
Grape soda	Grape Soda	❌
Mixed berry blue	Mixed Berry Blue	❌
Neutral Grey	Neutral Grey	✔️
Neutral default	Neutral Default	❌
Orange creamsicle	Orange Creamsicle	❌
Origami	Origami	✔️
Shirley temple	Shirley Temple	❌
Terminal	Terminal	✔️
Terminal Grayscale	Terminal Grayscale	✔️
Vanilla nitro cola	Vanilla Nitro Cola	❌
Dark Flagship Terrastruct	Dark Flagship Terrastruct	✔️
Dark Mauve	Dark Mauve	✔️

Associated Press Stylebook details

Capitalize:

• The first word
• The last word
• All nouns
• All pronouns
• All verbs
• All adjectives
• All adverbs
• All proper nouns and proper adjectives

Lowercase:

• Articles (a, an, the)
• Prepositions with three or fewer letters (at, by, for, from, in, of, on, to, with)
• Conjunctions with three or fewer letters (and, but, for, nor, or, so, yet)

Exceptions:

• Prepositions and conjunctions are capitalized if they are four letters or longer:
  "Through," "Against," "During"
• Prepositions and conjunctions are capitalized if they are the first or last word in the title:
  "Into the Woods," "Over and Out"
• "To" is capitalized when part of an infinitive:
  "Learn To Fly"