optionally move float emulation code into iram (#8958)

* optionally move float emulation code into iram
allows doing float operation in iram
suitable for libraries like AccelStepper when called from ISR
* proposed changes for pio from @mcspr

package/package_esp8266com_index.template.json

@@ -383,4 +383,4 @@
          ]
       }
    ]
-}
+}