Make the "smallest working example" actually work, see #553

[shish]

Make the "smallest working example" actually work, see #553

This example had implicit-and-undocumented dependencies on composer.json, and explicit-but-unexplained dependencies on "a container" and "a cache", leaving the installation and configuring of these as an exercise to the reader. I have changed it so that the example code can be copy-pasted verbatim, and the user will end up with an example which runs, which I find much easier to learn from :)

I'm still not actually sure if I'm doing this correctly, because #553 mentioned loading classes via the PSR-4 autoloader, and I found that it only worked when I manually listed out my controller classes inside the PSR-11 container, but it works...

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.29%. Comparing base (53f9d49) to head (98c0052). Report is 70 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #663 +/- ## ============================================ - Coverage 95.72% 95.29% -0.44% - Complexity 1773 1818 +45 ============================================ Files 154 171 +17 Lines 4586 4841 +255 ============================================ + Hits 4390 4613 +223 - Misses 196 228 +32 ```

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[oojacoboo]

Thanks for this @shish!

Let's stick with APCu in the example with a code comment for Filesystem, like #662.

[shish]

(I do wonder if it'd be worth having example code as actual code (either in an "examples" folder, or a "graphqlite-examples" respository), rather than random code snippets inside a markdown text file -- that way we can use eg github actions to run the code and ensure that it both works and stays working 🤔 )

[oojacoboo]

Let's update this PR such that the docs direct the reader to the examples, instead of maintaining any code here.

[oojacoboo]

Let's update this PR such that the docs direct the reader to the examples, instead of maintaining any code here.

@shish ^^