feat(plugins, keymaps): Add plugins, move plugins to nix, update keymaps

Added:
  - [aerial.nvim](https://github.com/stevearc/aerial.nvim)
  - [better-escape.nvim](https://github.com/max397574/better-escape.nvim)
  - [dressing.nvim](https://github.com/stevearc/dressing.nvim)
  - [ident-blankline.nvim](https://github.com/lukas-reineke/indent-blankline.nvim)
  - [nvim-notify](https://github.com/rcarriga/nvim-notify)
  - [todo-comments.nvim](https://github.com/folke/todo-comments.nvim)

Moved plugin source from Github to Nix:
  - [Comment.nvim](https://github.com/numToStr/Comment.nvim)
  - [neo-tree.nvim](https://github.com/numToStr/Comment.nvim)

Mapped windown switching to `<C-h`... instead of `<M-h`...
Moved some coliding lsp keymaps under the `<leader>l` group
  - Eg. `<leader>ls` for signature help

nvim/plugin/ident-blankline.lua

@@ -0,0 +1,33 @@
+if vim.g.did_load_ibl_plugin then
+  return
+end
+vim.g.did_load_ibl_plugin = true
+
+local highlight = {
+    "RainbowRed",
+    "RainbowYellow",
+    "RainbowBlue",
+    "RainbowOrange",
+    "RainbowGreen",
+    "RainbowViolet",
+    "RainbowCyan",
+}
+
+local hooks = require "ibl.hooks"
+-- create the highlight groups in the highlight setup hook, so they are reset
+-- every time the colorscheme changes
+hooks.register(hooks.type.HIGHLIGHT_SETUP, function()
+    vim.api.nvim_set_hl(0, "RainbowRed", { fg = "#E06C75" })
+    vim.api.nvim_set_hl(0, "RainbowYellow", { fg = "#E5C07B" })
+    vim.api.nvim_set_hl(0, "RainbowBlue", { fg = "#61AFEF" })
+    vim.api.nvim_set_hl(0, "RainbowOrange", { fg = "#D19A66" })
+    vim.api.nvim_set_hl(0, "RainbowGreen", { fg = "#98C379" })
+    vim.api.nvim_set_hl(0, "RainbowViolet", { fg = "#C678DD" })
+    vim.api.nvim_set_hl(0, "RainbowCyan", { fg = "#56B6C2" })
+end)
+
+require("ibl").setup{
+  indent = {
+    highlight = highlight
+  }
+}