Add examples/README.md (#55)

Describe each example program so readers can pick the right starting
point. Ordered simplest to most involved, matching the ponylang
examples convention.

Closes #48

Author: SeanTAllen

examples/README.md

@@ -0,0 +1,32 @@
+# Examples
+
+Each subdirectory is a self-contained Pony program demonstrating a
+different part of the ssl library. Ordered from simplest to most
+involved: the hashing examples come first, the SSL networking example
+follows.
+
+## [hash-fn-example](hash-fn-example/)
+
+Computes MD5, SHA1, and SHA256 hashes of a string in a single call each
+and prints the results. Shows the one-shot convenience functions `MD5`,
+`SHA1`, and `SHA256` from `ssl/crypto`, plus `ToHexString` for
+formatting the resulting `Array[U8] val`. Start here if you're new to
+the library.
+
+## [digest-example](digest-example/)
+
+Hashes data in chunks using the streaming `Digest` API. Creates a
+`Digest.sha256()`, appends two string pieces with `append()`, and
+finalizes with `final()` to produce the hash. Also demonstrates
+`Digest.shake256(n)` for variable-length output on OpenSSL 3.0.x and
+4.0.x, guarded by an `ifdef`.
+
+## [ssl-client-server-example](ssl-client-server-example/)
+
+Runs a TLS client and server in the same process, exchanging a few
+messages over a loopback TCP connection. Demonstrates setting up an
+`SSLContext` with `set_authority`, `set_cert`, and verification toggled
+off, then wrapping both sides of a `TCPConnection` with `SSLConnection`
+from `ssl/net`. Requires an `assets/cert.pem` and `assets/key.pem`
+alongside the example — see the source comments for how the relative
+paths are resolved.