docs: explain why typescript is added either way (#8484)

* docs: explain why typescript is added either way

for a library project
closes #8189

* add jsconfig for lib, closes #7475

* Update documentation/docs/30-advanced/70-packaging.md

* replace icon with warning sign

* changeset

* unicode warning symbol looks strangely shit - use a yellow triangle instead

* the bold does nothing

Co-authored-by: Rich Harris <richard.a.harris@gmail.com>
Co-authored-by: Rich Harris <hello@rich-harris.dev>

.changeset/slow-stingrays-hunt.md

@@ -0,0 +1,5 @@
+---
+'create-svelte': patch
+---
+
+fix: note why TypeScript is always installed for library projects and add jsconfig

documentation/docs/30-advanced/70-packaging.md

@@ -13,7 +13,7 @@ A component library has the exact same structure as a SvelteKit app, except that
 Running the `svelte-package` command from `@sveltejs/package` will take the contents of `src/lib` and generate a `package` directory (which can be [configured](/docs/configuration)) containing the following:
 
 - All the files in `src/lib`, unless you [configure](/docs/configuration) custom `include`/`exclude` options. Svelte components will be preprocessed, TypeScript files will be transpiled to JavaScript.
-- Type definitions (`d.ts` files) which are generated for Svelte, JavaScript and TypeScript files. You need to install `typescript >= 4.0.0` for this. Type definitions are placed next to their implementation, hand-written `d.ts` files are copied over as is. You can [disable generation](/docs/configuration), but we strongly recommend against it.
+- Type definitions (`d.ts` files) which are generated for Svelte, JavaScript and TypeScript files. You need to install `typescript >= 4.0.0` for this. Type definitions are placed next to their implementation, hand-written `d.ts` files are copied over as is. You can [disable generation](/docs/configuration), but we strongly recommend against it — people using your library might use TypeScript, for which they require these type definition files.
 - A `package.json` copied from the project root with all fields except `"scripts"`, `"publishConfig.directory"` and `"publishConfig.linkDirectory"`. The `"dependencies"` field is included, which means you should add packages that you only need for your documentation or demo site to `"devDependencies"`. A `"type": "module"` and an `"exports"` field will be added if it's not defined in the original file.
 
 The `"exports"` field contains the package's entry points. By default, all files in `src/lib` will be treated as an entry point unless they start with (or live in a directory that starts with) an underscore, but you can [configure](/docs/configuration) this behaviour. If you have a `src/lib/index.js` or `src/lib/index.svelte` file, it will be treated as the package root.

packages/create-svelte/bin.js

@@ -1,7 +1,7 @@
 #!/usr/bin/env node
 import fs from 'fs';
 import path from 'path';
-import { bold, cyan, gray, green, red } from 'kleur/colors';
+import { bold, cyan, gray, green, yellow } from 'kleur/colors';
 import prompts from 'prompts';
 import { create } from './index.js';
 import { dist } from './utils.js';
@@ -136,6 +136,11 @@ async function main() {
 	} else if (options.types === 'checkjs') {
 		console.log(bold('✔ Type-checked JavaScript'));
 		console.log('  https://www.typescriptlang.org/tsconfig#checkJs');
+	} else if (options.template === 'skeletonlib') {
+		const warning = yellow('▲');
+		console.log(
+			`${warning} You chose to not add type checking, but TypeScript will still be installed in order to generate type definitions when building the library`
+		);
 	}
 
 	if (options.eslint) {

packages/create-svelte/shared/+libskeleton-typescript/jsconfig.json

@@ -0,0 +1,11 @@
+{
+	"extends": "./.svelte-kit/tsconfig.json",
+	"compilerOptions": {
+		"esModuleInterop": true,
+		"forceConsistentCasingInFileNames": true,
+		"resolveJsonModule": true,
+		"skipLibCheck": true,
+		"sourceMap": true,
+		"moduleResolution": "NodeNext"
+	}
+}