Fix npm badge in mithril-client-wasm README files

[dlachaume]

Content

This PR includes a fix in the README files of mithril-client-wasm.

Pre-submit checklist

• Branch
  • Crates versions are updated (if relevant)
  • Commit sequence broadly makes sense
  • Key commits have useful messages
• PR
  • No clippy warnings in the CI
  • Self-reviewed the diff
  • Useful pull request description
  • Reviewer requested
• Documentation
  • Update README file (if relevant)

[jpraynaud]

LGTM 👍

[github-actions]

Test Results

  3 files  ±0   33 suites  ±0   8m 45s ⏱️ +19s
778 tests ±0  778 ✅ ±0  0 💤 ±0  0 ❌ ±0 
851 runs  ±0  851 ✅ ±0  0 💤 ±0  0 ❌ ±0 

Results for commit 4c852de. ± Comparison against base commit 88c59ab.

♻️ This comment has been updated with latest results.