Add an optional `[build]` table, only used for the "build" sub-command.
Supported entries.
- `paths = [..]` list of strings.
Explicitly list all paths to include.
Python "wheels" and the manifest are automatically included.
- `paths_exclude_pattern = [..]` list of strings.
A `.gitignore` compatible list of patterns.
By default "paths_exclude_pattern" is set to:
[".*", "__pycache__"] when the `[build]` table entry isn't found.
Only one of these options is supported at once since it makes to sense
to exclude paths when they're manually listed.
Use the name "index.json" instead of "bl_ext_repo.json".
This makes more sense as the name is automatically added to the end
of file:// URL's a little like index.html for web-sites.
Manually deleting the extensions directory caused checking for
updates on startup to fail.
It attempted to create a directory without the parent existing
which raised an error.
Previously regular paths were supported however supporting both
URL's and file paths isn't very common & complicated internal logic.
Also fixed an error where the server-generate sub-command created the
"archive_url" from the file-name without URL encoding.
