Add olwb (one-line-with-benefits) plugin

[TGPSKI]

This adds olwb ("one line with benefits") to the plugin channel.

olwb is a one-line-input notepad inside micro: type a line, press Enter, and it lands in a newest-first feed under the input with a timestamp and any active labels. Notes are grouped as Liner → Session → Message with label inheritance; there's filtering, search, and markdown/JSON export, all driven by slash commands with an in-editor menu and Tab completion. Storage is one JSON file per liner under $XDG_DATA_HOME/olwb, written atomically.

Following the "Adding your own plugin" guide:

• Adds plugins/olwb.json with the version zip pointed at the plugins release: https://github.com/micro-editor/plugin-channel/releases/download/plugins/olwb-1.1.0.zip (requires micro >= 2.0.0)
• channel.json links to plugins/olwb.json in this repository
• Zip to upload to the plugins release: olwb-1.1.0.zip (attached to the plugin's v1.1.0 release; same layout as the other plugin zips, LICENSE included)
• License: MIT (LICENSE in the repo and License field in the JSON)
• Repository: https://github.com/TGPSKI/olwb-micro-plugin (with its own repo.json)

Pure Lua; the only third-party code is a vendored copy of rxi/json.lua (MIT). The plugin registers its own help (> help olwb), syntax file, and an optional colorscheme; all keybinds are overridable and its buffers are scratch panes under olwb:// paths. Screenshots are in the comment below.

[TGPSKI]