strange parse error for `+.( ... )`

[JeffBezanson]

Was just looking at #20540 and noticed this:

julia> +.(1,2)
ERROR: syntax: numeric constant "." cannot be implicitly multiplied because it ends with "."

At the very least, the error message doesn't make sense.

### Tasks

[JeffBezanson]

Noticed in a different form here: #32860 (comment)

julia> +.
ERROR: LoadError: ArgumentError: invalid base 10 digit '.' in "."

Because + can be part of numeric literals, we try to parse the dot as one. For example +.1 works. We should do what non-numeric-literal unary operators do:

julia> !.
ERROR: syntax: invalid identifier name "."

[brenhinkeller]

Still reproduces in 1.8.3

[adienes]

We should do what non-numeric-literal unary operators do

this is now the observed behavior now with JuliaSyntax merged.

julia> +.
ERROR: ParseError:
# Error @ REPL[7]:1:2
+.
#╙ ── invalid identifier
Stacktrace:
 [1] top-level scope
   @ none:1

[vtjnash]

This could use a test, if you would be willing to write one.