Add docs pages for fixing CVE-2025-69872 and migrating from diskcache 5.6.3

[avgvi]

Two new documentation pages, placed first in the table of contents and linked from the README.

Fix CVE-2025-69872 in diskcache (docs/fix-cve-2025-69872.rst)

• Opens with the install command and Cache(..., disk=SafeDisk).
• What the vulnerability is and who is exposed (anyone else who can write into the cache directory).
• Steps: move to the fork, select SafeDisk for your caches and for caches libraries create (DISKCACHE_DISK=safe or configure, which reaches only caches created through diskcache_community), allow your own classes with with_types, store numpy arrays as bytes, handle entries already in the cache (clear() or on_error='miss'), and check the result.
• What stays the same: the default Disk still uses pickle.load, and a clean scanner result says nothing about which disk a cache uses.
• A checklist of what any restricted disk has to cover, with how SafeDisk handles each item: keys as well as values, the filename column, exact classes rather than module prefixes, no numpy, no imports while reading, and refusal at write time.

Migrating from diskcache 5.6.3 (docs/migrating.rst)

• The dependency, the imports (exceptions and Disk subclasses included), the Django settings, and a test run against an existing cache.
• Running next to the upstream diskcache package, with the try/except import for libraries.
• The behaviour changes since 5.6.3: 0700 directories, read-only opening, the SQLITE_DQS=0 trigger rewrite, memoize keys for ignored positional parameters, connection and fork handling, FanoutCache fixes, and the None disk default.
• Going back to 5.6.3.

doc8 passes and the Sphinx build is clean.

[read-the-docs-community]

Documentation build overview

📚 diskcache-community | 🛠️ Build #35229040 | 📁 Comparing 45d8fd1 against latest (19876af)

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3 files changed

+ fix-cve-2025-69872.html
+ migrating.html
± index.html