docs: call displayio.release_displays() before SPI init in README example (fixes #39)

[ritesh006]

What

Move displayio.release_displays() above SPI initialization in the README example and add a brief comment explaining why.

Why

Initializing SPI before displayio.release_displays() can leave pins “in use” on subsequent reloads of code.py, especially when users switch to explicit busio.SPI(...) pins. This change prevents those errors. Fixes #39.

Changes

• README.rst: call displayio.release_displays() before spi = board.SPI()
• Add comment:

  If you use explicit pins with busio.SPI(...), calling release_displays() first

  prevents "pin in use" errors on subsequent reloads.

Scope

Docs-only; no runtime code changes.

How to Verify

1. Flash the README example to a board with an ILI9341.
2. Save once → display initializes.
3. Modify and re-save (or reset) → no “pin in use” errors on reload.

[ritesh006]

Docs tweak for #39: move displayio.release_displays() above SPI init to avoid pin conflicts on reload.
Ready for review—thanks in advance!

[FoamyGuy]

Thank you!