Adds a short tProc v2 migration guide under the docs topics section.

[JayChien04717]

Adds a short tProc v2 migration guide under the docs topics section.

The guide covers:

hardware sweeping changes from tProc v1 to v2
timing terminology updates
pulse playback changes
natural units used by the tProc v2 API

[lharnaldi]

Thanks for this, @JayChien04717 — the migration guide and example-code list are both genuinely useful additions and were missing from our docs.

We recently restructured the docs tree from a flat docs/*.rst layout to docs/source/ (as part of a broader tProc v2 documentation pass, see #430), which is why this PR no longer applies cleanly against main. Rather than ask you to rebase across that restructuring, I've ported your content into the new tree with credit in #430:

• docs/source/topics/tprocv2_migration.rst (your migration guide)
• docs/source/topics/example_code.rst (your example-code list, with the Markdown-style headings/links fixed to valid RST)

Both are wired into docs/source/topics/index.rst and verified against the current API. Closing this one in favor of that — thanks again for the contribution!