fix: Provide meaningful error message when signature verification fai…

…ls (#197)

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## What type of PR is this? (check all applicable)

- [ ] 🍕 Feature
- [x] 🐛 Bug Fix
- [ ] 📝 Documentation Update
- [ ] 🎨 Style
- [ ] 🧑‍💻 Code Refactor
- [ ] 🔥 Performance Improvements
- [ ] ✅ Test
- [ ] 🤖 Build
- [ ] 🔁 CI
- [ ] 📦 Chore (Release)
- [ ] ⏩ Revert

## Description
I found something regarding this issue. If you want to know more, please
read the comment in the attached ticket below.<!--
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This PR [adds/removes/fixes/replaces] the [feature/bug/etc]. 
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gs-gs/fa-ag-trace#476
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src="https://github.com/uncefact/project-vckit/assets/59736798/8219d4ff-d902-4119-8c9d-cb43c108a668">

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## Added tests?

- [ ] 👍 yes
- [x] 🙅 no, because they aren't needed
- [ ] 🙋 no, because I need help

## Added to documentation?

- [ ] 📜 README.md
- [ ] 📓 [vc-kit doc site](https://uncefact.github.io/vckit/)
- [ ] 📕 storybook
- [x] 🙅 no documentation needed

## [optional] Are there any post-deployment tasks we need to perform?


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packages/demo-explorer/src/pages/CredentialVerifier.tsx

@@ -75,11 +75,16 @@ const CredentialVerifier = () => {
           credential: JSON.parse(text),
           fetchRemoteContexts: true,
         })
-        setVerificationResult(result)
+
         if (result?.verified) {
-          setVerificationResult((result) => {
-            if (!result) return result
-            return { ...result, verifiableCredential: JSON.parse(text) }
+          setVerificationResult({
+            ...result,
+            verifiableCredential: JSON.parse(text),
+          })
+        } else {
+          setVerificationResult({
+            verified: false,
+            error: { message: JSON.stringify(result?.error, null, 2) },
           })
         }
       } catch (e: any) {