Convert docs and types scripts to .mjs to fix node errors on some platforms

[davepagurek]

While this was working for me on Mac before, I was getting this warning when running generate-types or docs:

(node:92436) [MODULE_TYPELESS_PACKAGE_JSON] Warning: Module type of file:///Users/dpagurek/Documents/Projects/p5.js-2/utils/convert.js is not specified and it doesn't parse as CommonJS.
Reparsing as ES module because module syntax was detected. This incurs a performance overhead.

Meanwhile, @perminder-17 was getting an actual error from this, even on node 20+, which I was only seeing on node 18:

(node:39622) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension.
(Use `node --trace-warnings ...` to show where the warning was created)
/home/perminder/Desktop/documentation-project/new-one/p5.js/utils/convert.js:1
import fs from 'fs';
^^^^^^

SyntaxError: Cannot use import statement outside a module
    at internalCompileFunction (node:internal/vm:73:18)
    at wrapSafe (node:internal/modules/cjs/loader:1187:20)
    at Module._compile (node:internal/modules/cjs/loader:1231:27)
    at Module._extensions..js (node:internal/modules/cjs/loader:1321:10)
    at Module.load (node:internal/modules/cjs/loader:1125:32)
    at Module._load (node:internal/modules/cjs/loader:965:12)
    at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:83:12)
    at node:internal/main/run_main_module:23:47

Rather than convert the whole project to a module, which might have downstream implications on the src/ folder, I've just updated the scripts that use import to be .mjs.