feat: add support for cjs

[tmm1]

want to import this package in a nodejs environment where commonjs modules are being used

[tmm1]

this worked, but now i'm having the same issue with the uint8arrays dependency. from the project where i'm trying to use this:

@connectrpc/connect-node:test:     Failed: require() of ES Module node_modules/uint8arrays/dist/src/alloc.node.js from node_modules/uint8arraylist/dist/cjs/src/index.js not supported.
@connectrpc/connect-node:test:     Instead change the require of alloc.node.js in node_modules/uint8arraylist/dist/cjs/src/index.js to a dynamic import() which is available in all CommonJS modules.
@connectrpc/connect-node:test:   Stack:
@connectrpc/connect-node:test:     error properties: Object({ code: 'ERR_REQUIRE_ESM' })
@connectrpc/connect-node:test:         at Object.<anonymous> (node_modules/uint8arraylist/dist/cjs/src/index.js:87:17)
@connectrpc/connect-node:test:         at Object.<anonymous> (packages/connect/dist/cjs/protocol/async-iterable.js:65:26)
@connectrpc/connect-node:test:         at Object.<anonymous> (packages/connect/dist/cjs/callback-client.js:28:29)
@connectrpc/connect-node:test:         at Object.<anonymous> (packages/connect/dist/cjs/index.js:25:28)
@connectrpc/connect-node:test:         at Object.<anonymous> (packages/connect-node/dist/cjs/http2-session-manager.js:18:19)
@connectrpc/connect-node:test:         at Object.<anonymous> (packages/connect-node/dist/cjs/testdata/http2-session-manager-verify-ping.js:17:36)