fix: unambiguous repo key names, clearer config and key names, and a newer lazysecrets's files no longer stop an older one (#66)

Changes that would break configs or links once people use lazysecrets, made while nobody does yet.

- **Repo key names**: a dot or bracket inside a key is escaped (`app\.name`), so links to it resolve to that key and not to `app` → `name`. Dotenv files are flat, so their names stay as they are.
- **Config**: `updates.updateSources` is now `updates.sources`. A negative provider timeout, or `--timeout` of 0 or less, is an error instead of making every request fail.
- **Keybindings**: `lists.share` is now `lists.copyLink`, `lists.search` is `lists.goTo` and `lists.enter` is `lists.open`, matching what they do.
- **Version skew**, e.g. a lazysecrets.nvim theme file made for a newer lazysecrets:
  - an unknown theme role is skipped with a warning instead of stopping startup;
  - a state file from a newer version is read but not saved to, with a warning;
  - a link with an unknown provider suggests `lazysecrets update`.

Reviewed-on: #66
Co-authored-by: Karl-Einar Bergstrøm <karl-einarb@outlook.com>

docs/repos.md

@@ -3,7 +3,8 @@
 lazysecrets shows git repositories under **Repos**: their
 [SOPS](https://github.com/getsops/sops)-encrypted files (YAML, JSON,
 `.env`, INI) and plain env files as vaults, and the keys in them
-(`db.password`, `list[0]`) as secrets.
+(`db.password`, `list[0]`) as secrets. A dot or bracket inside a key is
+escaped, `app\.name`, so it doesn't read as nesting.
 
 ## Which repos