feat: post-conditions

[manuel3108]

Closes #337 (preconditions already implemented by #368)

Usage:

export const checks = defineAdderChecks({
    options,
    postconditions: [
        {
            name: "scss setup",
            run: async ({ fileExists, fileContains }) => {
                if (options.useSass) {
                    const filePath = `src/variables.scss`;
                    await fileExists(filePath);
                    await fileContains(filePath, "$background: lightgrey;");
                }
            },
        },
    ],
});

Will be helpful for all adders that we cannot check with integration testing, like #338, #339 , etc.

This is currently not implemented for any adder, as all adders are currently testable by integration testing. Future adders will use this feature.

Console output looks like this:

[changeset-bot]

🦋 Changeset detected

Latest commit: 6df0f79

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 11 packages

Name	Type
@svelte-add/core	Minor
svelte-add	Patch
@svelte-add/testing-library	Patch
@svelte-add/website	Patch
@svelte-add/bootstrap	Patch
@svelte-add/bulma	Patch
@svelte-add/mdsvex	Patch
@svelte-add/routify	Patch
@svelte-add/storybook	Patch
@svelte-add/tailwindcss	Patch
@svelte-add/threlte	Patch

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[manuel3108]

@AdrianGonz97 Would you mind reviewing this, even if this is not directly testable?

[AdrianGonz97]

Code-wise everything looks good! although, I do have a few questions:

So if a postcondition fails for a user, what are the actionable steps that a user should take when an error is thrown? Should it tell the user how to fix it (if it can be fixed)? Should it provide a link to our issue tracker and ask them to raise an issue?

[manuel3108]

Good catch. I added an appropriate text to inform the user that they should create an issue.