docs: add examples for common usecases

README.md

@@ -86,3 +86,37 @@ the [utf8proc issues page on Github](https://github.com/JuliaLang/utf8proc/issue
 ## See also
 
 An independent Lua translation of this library, [lua-mojibake](https://github.com/differentprogramming/lua-mojibake), is also available.
+
+## Examples
+
+### Convert codepoint to string
+```c
+// Convert codepoint `a` to utf8 string `str`
+utf8proc_int32_t a = 223;
+utf8proc_uint8_t str[16] = { 0 };
+utf8proc_encode_char(a, str);
+printf("%s\n", str);
+// ß
+```
+
+### Convert string to codepoint
+```c
+// Convert string `str` to pointer to codepoint `a`
+utf8proc_uint8_t str[] = "ß";
+utf8proc_int32_t a;
+utf8proc_iterate(str, -1, &a);
+printf("%d\n", a);
+// 223
+```
+
+### Casefold
+
+```c
+// Convert `ß` to its casefold variant `ss`
+utf8proc_uint8_t str[] = "ß";
+utf8proc_uint8_t *fold_str;
+utf8proc_map(str, 0, &fold_str, UTF8PROC_NULLTERM | UTF8PROC_CASEFOLD);
+printf("%s\n", fold_str);
+// ss
+free(fold_str);
+```