feat: add Nim syntax test file

tests/syntax-tests/source/nim/main.nim

@@ -0,0 +1,41 @@
+import json
+
+const
+  message = "hello world"
+  multiLine = """
+    foo
+    bar
+  """
+  numbers = @[1, 2, 3]
+
+type Options = enum
+  A,
+  B,
+  C
+
+## Top-level comment
+type
+  SomeStruct* = ref object
+    value*: string
+
+proc someFunc*(): string =
+  ## Function docs
+  ##
+  ## More docs
+  result = message
+
+proc someOtherFunc(startingValue: int): (string, int) =
+  var num = startingValue
+  num += 1
+  if num > 10 * 10 * 10:
+    echo "Encountered an error"
+    raise newException(ValueError, "Value was over 1000")
+  ("Fizz", num)
+
+proc `+=`(a: var SomeStruct, b: SomeStruct): string =
+  a.value.add(b.value)
+  return a.value
+
+echo someFunc()
+echo(someOtherFunc(123))
+discard someFunc()