Add libsql-conformance to the README and CONTRIBUTING module inventory #170

Problem

README.md §Modules and CONTRIBUTING.md §Project Structure list only four modules (libsql-jdbc, libsql-client, libsql-hrana-codec, libsql-itests). The fifth module, libsql-conformance, is missing from both even though it is a first-class module in the root pom.xml and has its own README.

AGENTS.md §2 already lists all five. The three documents disagree.

Proposed change

• Add libsql-conformance to the README.md module table with a one-line description and a link to libsql-conformance/README.md.
• Add libsql-conformance to the CONTRIBUTING.md project-structure list.
• Make the three inventories consistent in order and wording.

Acceptance criteria

• README.md, CONTRIBUTING.md, and AGENTS.md all name the same five modules.
• README.md links to libsql-conformance/README.md.