Update README.md

README.md

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 # constexpr-to-string
-C++17 code to convert integers to strings at compile-time
+
+**Features:**
+
+* Convert any integral type to a string at compile-time
+* String can be in binary, hexadecimal, or any base in-between
+* No external dependencies, only includes `type_traits` for type-checking
+* Works best in C++20 GCC or C++17/20 Clang
+
+**How to use:**
+
+This single header file provides a `to_string` utility, which may be used as below:
+
+```cpp
+const char *number = to_string<2147483648999954564, 16>; // produces "1DCD65003B9A1884"
+puts(number);
+puts(to_string<-42>); // produces "-42"
+puts(to_string<30, 2>); // produces "11110"
+```
+
+With `to_string`, all that will be found in program disassembly are the resulting string literals, as if you wrote the strings yourself.
+
+**Known issues:**
+
+* With C++17 GCC, `to_string` must be used to initialize variables; otherwise, the integer-string conversion is done at run-time.