[Plugins in Rust] inconsistent cargo run examples

[wlthomson]

As others have already said, thanks for providing this tutorial. It's been very helpful.

Just a minor issue: the example cargo run commands load different libplugins_random.so builds (target/release vs. target/debug):

$ cargo run -- ../target/release/libplugins_random.so random
...

cargo run -- ../target/debug/libplugins_random.so random
...

Although I assume it doesn't make any difference in practice, the inconsistency adds potential for confusion. To remove any ambiguity, it might be worth prefacing these examples with instructions for (re)building the executable and libraries.

[wlthomson]

Migrated from Michael-F-Bryan/plugins_in_rust#4.