feat: Move all of popup into plenary (nvim-lua#209)

* feat: Move all of popup into plenary

* fixup: Add lint that only certain plenary modules can be required

* fixup: stylua

* fixup: Update test to search for both types of requires

* fixup: Add readme

* fixup: Update readme

POPUP.md

@@ -0,0 +1,86 @@
+# Popup tracking
+
+[WIP] An implementation of the Popup API from vim in Neovim. Hope to upstream
+when complete
+
+## Goals
+
+Provide an API that is compatible with the vim `popup_*` APIs. After
+stablization and any required features are merged into Neovim, we can upstream
+this and expose the API in vimL to create better compatibility.
+
+## List of Neovim Features Required:
+
+- [ ] Add Z-index for floating windows
+    - [ ] When complete, we can add `zindex` parameter
+- [ ] Key handlers (used for `popup_filter`)
+- [ ] scrollbar for floating windows
+    - [ ] scrollbar
+    - [ ] scrollbarhighlight
+    - [ ] thumbhighlight
+
+Optional:
+
+- [ ] Add forced transparency to a floating window.
+    - Apparently overrides text?
+    - This is for the `mask` feature flag
+
+
+Unlikely (due to technical difficulties):
+
+- [ ] Add `textprop` wrappers?
+    - textprop
+    - textpropwin
+    - textpropid
+- [ ] "close"
+    - But this is mostly because I don't know how to use mouse APIs in nvim. If someone knows. please make an issue in the repo, and maybe we can get it sorted out.
+
+Unlikely (due to not sure if people are using):
+- [ ] tabpage
+
+## Progress
+
+Suported Features:
+
+- [x] what
+    - string
+    - list of strings
+- [x] popup_create-arguments
+    - [x] border
+    - [x] borderchars
+    - [x] col
+    - [x] cursorline
+    - [x] highlight
+    - [x] line
+    - [x] {max,min}{height,width}
+    - [?] moved
+        - [x] "any"
+        - [ ] "word"
+        - [ ] "WORD"
+        - [ ] "expr"
+        - [ ] (list options)
+    - [x] padding
+    - [?] pos
+        - Somewhat implemented. Doesn't work with borders though.
+    - [x] posinvert
+    - [x] time
+    - [x] title
+    - [x] wrap
+
+## All known unimplemented vim features at the moment
+
+- firstline
+- hidden
+- ~ pos
+- fixed
+- filter
+- filtermode
+- mapping
+- callback
+- mouse:
+    - mousemoved
+    - close
+    - drag
+    - resize
+
+- (not implemented in vim yet) flip

README.md

@@ -284,10 +284,7 @@ Status: WIP
 
 ### plenary.popup
 
-`popup_*` clone of Vim's commands. If it gets good enough, will submit PR to Neovim and write C wrappers
-to provide compatibility layer for Neovim.
-
-Status: WIP
+See [popup documentation](./POPUP.md) for both progress tracking and implemented APIs.
 
 ### plenary.window