Concise type signatures

[LightAndLight]

When I define constants in a script, I have to type the constant name twice:

binaryCacheBucket : String
binaryCacheBucket = "ipso-binary-cache"

binaryCacheEndpoint : String
binaryCacheEndpoint = "7065dc7f7d1813a29036535b4c4f4014.r2.cloudflarestorage.com"

(taken from #271)

Key strokes are valuable in short scripts. I'd rather write something like this:

binaryCacheBucket : String = "ipso-binary-cache"
binaryCacheEndpoint : String = "7065dc7f7d1813a29036535b4c4f4014.r2.cloudflarestorage.com"

This also applies to function definitions. Instead of

plus : Int -> Int -> Int
plus m n = m + n

I can write

plus (m : Int) (n : Int) : Int = m + n

[LightAndLight]

I think we should start by allowing definitions of the form identifier : Type = expression, and leaving the syntax of function definitions unchanged. Allowing identifier : Type = expression is a backwards compatible change and is an improvement in itself.