Add Deno installation commands

[mintydev789]

The installation instructions have commands for installing via NPM, Yarn, PNPM and Bun, but not Deno, which would also be useful. These commands should be added for an installation instructions tab for Deno:

deno add --npm --allow-scripts drizzle-orm pg dotenv
deno add -D --npm --allow-scripts drizzle-kit tsx @types/pg

Equivalent installation instructions should be added for the other DB providers too. I'm happy to open up a PR to add all of these, if necessary.