Photo: one async method per EXIF field (closes #148)

Thirteen methods on Photo, make() through gpsAltitude(), each named after
its PhotoExif field and typed by it. Each calls exif() with the same opts
and returns that one field, or undefined when the file lacks it. A test
checks, on the JPEG fixture and on test/exif.heic, that every field
exif() returns has a method giving the same value. README and TODO.md
list them.

Model: opus-5-5

README.md

@@ -711,7 +711,7 @@ synchronous getters look at the disk and never touch the network:
   or no content source.
 - `photo.isLocal` → `boolean` — whether the whole original is at `savePath`.
 
-Four async methods may download:
+These async methods may download:
 
 - `await photo.original(opts?)` → `{ path, bytes, videoPath? }` — the
   full-resolution file. For a live photo, `path` and `bytes` are its image's and
@@ -728,6 +728,12 @@ Four async methods may download:
   UTC. EXIF is read from any image format exifreader reads (such as JPEG,
   HEIC/HEIF, AVIF, PNG, WebP and TIFF), a live photo's image included. Any other
   original gives `{}`, and a video gives `{}` without being downloaded.
+- `await photo.make(opts?)`, and likewise `model()`, `lensModel()`,
+  `dateTimeOriginal()`, `offsetTimeOriginal()`, `exposureTime()`, `fNumber()`,
+  `iso()`, `focalLength()`, `orientation()`, `gpsLatitude()`, `gpsLongitude()`
+  and `gpsAltitude()` → one field of `exif()` each, typed as in `PhotoExif`, or
+  `undefined` when the file lacks it. Each calls `exif()` with its `opts`, so
+  each call reads the original again.
 
 They serve from the on-disk content cache when the bytes are present and
 otherwise fetch through the pools; `original()`, `content()` and `exif()` also