Newer serialization macros not listed in README

[gregmarr]

Description

As described in #4235 , the README only lists NLOHMANN_DEFINE_TYPE_NON_INTRUSIVE and NLOHMANN_DEFINE_TYPE_INTRUSIVE. There are now 6 macros.

There is documentation for these other 4, so it could just link to the documentation for more info on the other 4, rather than expanding the examples to cover all of them.

Also, only the two mentioned in the readme have @brief macro tags, rather than all 6, and the order of the intrusive versions doesn't match the order of the non-intrusive versions.

Reproduction steps

n/a

Expected vs. actual results

n/a

Minimal code example

No response

Error messages

No response

Compiler and operating system

n/a

Library version

a259ecc51e1951e12f757ce17db958e9881e9c6c

Validation

• [X] The bug also occurs if the latest version from the develop branch is used.
• [X] I can successfully compile and run the unit tests.