docs: apply v1.19.0 release updates - #11101

Summary

Completes the v1.19.0 post-release documentation process by publishing the release notes, clearing the pre-release changelog, and applying all deferred documentation updates across the README and documentation site.

Linked issue

N/A

Changes

• Add the v1.19.0 release notes to CHANGELOG.md and clear PRE_RELEASE_CHANGELOG.md.
• Document typed request params, synchronous interceptor errors, AxiosHeaders.parseParameters(), malformed HTTP(S) URL rejection, symbol-keyed config, and FormData key parsing.
• Synchronize the English, Spanish, French, and Chinese documentation.
• Correct HTML form examples so only dot and bracket notation create nested paths.
• Mark all entries in PRE_RELEASE_DOCS.md as applied.

Checklist

• Tests added or updated (N/A: documentation and release metadata only; the docs build, TypeScript examples, and 87 focused unit tests pass)
• Docs/types updated if public API changed (index.d.ts and index.d.cts were updated by the original feature changes; this PR synchronizes the documentation)
• No breaking changes (this PR only updates documentation and release metadata; the previously shipped URL behavior change is called out in the upgrade guide)

Summary by cubic

Publishes v1.19.0 release notes and syncs post‑release docs across README and all locales. Finalizes TypeScript generics, URL validation, interceptor error flow, and header parsing docs.

Description

• Summary of changes
  • Add v1.19.0 notes to CHANGELOG.md; remove stray control character; clear PRE_RELEASE_CHANGELOG.md; mark PRE_RELEASE_DOCS.md items as applied.
  • Update README.md and docs (en/es/fr/zh) to cover:
    • Callable axios<T, R, D, P>(url | config, config?); preserve D and P on response.config.
    • Typed params P across public types (AxiosRequestConfig, AxiosResponse, AxiosPromise, errors, adapters, serializers).
    • AxiosHeaders.parseParameters() and headers.get(name, AxiosHeaders.parseParameters) overload; align get signature/returns across locales.
    • Synchronous request interceptor error handling and when rejections block dispatch.
    • Rejection of malformed http:/https: URLs missing // in both url and baseURL (ERR_INVALID_URL); upgrade‑guide entries.
    • formToJSON() and HTML form parsing: only dot/bracket notation creates paths.
  • Changelog notes form-data@^4.0.6 floor for CRLF advisory.
• Reasoning
  • Finalize and publish v1.19.0 documentation to match shipped behavior and TypeScript APIs.
• Additional context
  • Docs-only; no runtime changes.

Docs

Update /docs/ and README.md, then redeploy the docs site to publish the v1.19.0 updates.

Testing

No tests added or modified. Build/preview the docs and run TypeScript checks on code samples.

Semantic version impact

None. Documentation-only changes.

^{Written for commit 8489409. Summary will update on new commits.}