refactor: structure refactor and docs improvements. (#518)

* init

* stage

* refactor: big changes

* fix: links

* refactor: sub0 page

* fix: revert changes of version in migration docs and remove ethereum tutorials because moved to docs.

* fix: removed unused files

* fix: sidebar looks

* fix: sidebar looks p2

* fix: solidity related comments david

* refactor: sidebar & redirect

* fix: ci

Author: Daanvdplas

docs/datastructures/custom.md renamed to docs/advanced/datastructures/custom.md

@@ -132,9 +132,9 @@ element is calculated as follows:
 `StorageVec` is a `Lazy` type similar to `Mapping`.
 
 Hence, the same considerations apply to `StorageVec` too:
-- [Storage loading behavior](../datastructures/mapping.md#storage-loading-behavior)
-- [Use fallible storage methods for dynamically sized values](../datastructures/mapping.md#use-fallible-storage-methods-for-dynamically-sized-values)
-- [Updating values](../datastructures/mapping.md#updating-values)
+- [Storage loading behavior](./mapping.md#storage-loading-behavior)
+- [Use fallible storage methods for dynamically sized values](./mapping.md#use-fallible-storage-methods-for-dynamically-sized-values)
+- [Updating values](./mapping.md#updating-values)
 
 ## Rust Docs
 

docs/datastructures/mapping.md renamed to docs/advanced/datastructures/mapping.md

@@ -24,16 +24,16 @@ Learn more about ink!'s support for multiple ABIs [here][abi-support].
 
 [sol-abi]: https://docs.soliditylang.org/en/latest/abi-spec.html
 [sol-abi-selector]: https://docs.soliditylang.org/en/latest/abi-spec.html#function-selector
-[abi-support]: ../basics/abi/overview.md
-[abi-declaration]: ../basics/abi/overview.md#declaring-the-abi
+[abi-support]: ../reference/abi/overview.md
+[abi-declaration]: ../reference/abi/overview.md#declaring-the-abi
 
 # Selectors
 
 Selectors in ink! are a language agnostic way of identifying constructors and messages.
 They are four-byte hexadecimal strings which look something like: `0x633aa551`.
 
 You can find the selector of an ink! constructor or message in your
-[contract metadata](./metadata/overview.md) by looking for the `selector` field of the dispatchable
+[contract metadata](../reference/metadata/overview.md) by looking for the `selector` field of the dispatchable
 you're interested in.
 
 Here is an example of how you can grab the message name and selector from your contract