Default import statements

[felix-hilden]

Discussed in #29: let's do it. I somewhat overlooked their utility in a bunch of small code blocks. The indirection is minimal, and any name clashes are resolved anyway. Perhaps something like:

# conf.py
codeautolink_default_imports = ["import lib", "import lib.sub as s"]

As with implicit-imports, we'll not allow newlines in entries.

[felix-hilden]

Nah, we'll split the lines just to be nice 👍

And why complicate things? We can just use a bare string and split that. Then the folks that want multiple imports can write a longer statement. _{and it could also include arbitrary code 🤫} Let's make the name singular as well.

[Zac-HD]

If it's not just a single import, let's name it accordingly - e.g. codeautolink_block_prelude

[felix-hilden]

That's a fun suggestion 😄 I kinda like it! But I think ideally this would also relate to implicit-imports. If you wouldn't mind we could continue the discussion in #27 where I'm about to rename a bunch of things. I'll add yours there, but for now I'll give it a similar "import" name.