Determines whether the specified code point is a base character. true for general categories "L" (letters),
"N" (numbers), "Mc" (spacing combining marks), and "Me" (enclosing marks).
Note:
This is different from the Unicode definition in chapter 3.5, conformance clause D13, which defines base characters
to be all characters (not Cn) that do not graphically combine with preceding characters (M) and that are neither
control (Cc) or format (Cf) characters.
Parameters
codepoint
The int codepoint value (e.g. 0x2603 for U+2603 SNOWMAN), or the character encoded as a UTF-8 string (e.g. "\u{2603}")
Return Values
Returns true if
codepoint is a base character, false if not. Returns null on failure.