Add documentation to README

Author: Taucher2003

README.md

@@ -18,3 +18,51 @@ Or install it yourself as:
 ```bash
 $ gem install code0-zero_track
 ```
+
+## Features
+
+### `Code0::ZeroTrack::Context`
+
+Context allows you to save data in a thread local object. Data from the Context is merged into the
+log messages, if `Code0::ZeroTrack::Logs::JsonFormatter` or `Code0::ZeroTrack::Logs::JsonFormatter::Tagged`
+is used.
+
+`.with_context(data, &block)` creates a new context inheriting data from the previous context and adds the
+passed data to it. The new context is dropped after the block finished execution. \
+`.push(data)` creates a new context inheriting data from the previous context and adds the passed data to it. \
+`.current` returns the context from the top of the stack.
+
+### `Code0::ZeroTrack::Memoize`
+
+This module can be included to get access to the `memoize(name, reset_on_change, &block)` method.
+
+This method allows to memoize a value, so it only gets computed once.
+Each memoize is identified by the name. You can pass a proc to `reset_on_change` and the memoization
+will automatically clear every time returned value changes.
+
+`memoized?(name)` allows to check if a value for the given name is currently memoized. \
+Memoizations can be cleared with `clear_memoize(name)` or `clear_memoize!(name)`.
+
+### `config.zero_track.active_record.schema_cleaner`
+
+When using `config.active_record.schema_format = :sql`, Rails produces a `db/structure.sql`.
+This file contains a lot of noise that doesn't provide much value.
+
+This noise can be cleaned out with `config.zero_track.active_record.schema_cleaner = true`.
+
+### `config.zero_track.active_record.timestamps`
+
+Setting `config.zero_track.active_record.timestamps = true` adds `timestamps_with_timezone`
+and `datetime_with_timezone` as methods on the table model when creating tables in migrations.
+
+They behave just like `timestamps` and `datetime`, just including timezones.
+
+### `config.zero_track.active_record.schema_migrations`
+
+Rails uses the `schema_migrations` table to keep track which migrations have been executed.
+This information is also persisted in the `db/structure.sql`, so the `schema_migrations` table
+can be filled with the correct entries when the schema is loaded from the schema file.
+
+This approach is prone to git conflicts, so you can switch to a file based persistence
+with `config.zero_track.active_record.schema_migrations = true`. Instead of an `INSERT INTO` in
+the `db/structure.sql`, this mode creates files in the `db/schema_migrations` directory.