docs: migrating docs from readme

docs/usage/migration.md

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+# 📦 Migration Guide
+
+## [packer.nvim](https://github.com/wbthomason/packer.nvim)
+
+- `setup` ➡️ `init`
+- `requires` ➡️ `dependencies`
+- `as` ➡️ `name`
+- `opt` ➡️ `lazy`
+- `run` ➡️ `build`
+- `lock` ➡️ `pin`
+- `disable=true` ➡️ `enabled = false`
+- `tag='*'` ➡️ `version="*"`
+- `after` is **_not needed_** for most use-cases. Use `dependencies` otherwise.
+- `wants` is **_not needed_** for most use-cases. Use `dependencies` otherwise.
+- `config` don't support string type, use `fun(LazyPlugin)` instead.
+- `module` is auto-loaded. No need to specify
+- `keys` spec is [different](#%EF%B8%8F-lazy-key-mappings)
+- `rtp` can be accomplished with:
+
+```lua
+config = function(plugin)
+    vim.opt.rtp:append(plugin.dir .. "/custom-rtp")
+end
+```
+
+With packer `wants`, `requires` and `after` can be used to manage dependencies.
+With lazy, this isn't needed for most of the Lua dependencies. They can be installed just like normal plugins
+(even with `lazy=true`) and will be loaded when other plugins need them.
+The `dependencies` key can be used to group those required plugins with the one that requires them.
+The plugins which are added as `dependencies` will always be lazy-loaded and loaded when the plugin is loaded.
+
+## [paq-nvim](https://github.com/savq/paq-nvim)
+
+- `as` ➡️ `name`
+- `opt` ➡️ `lazy`
+- `run` ➡️ `build`