feat(nvim): Markdown: QoL plugins and settings

- Link creation: autocommand to add <leader>ml shortcut for converting
  selected text to link
- Formatting: Use markdown-toc to format available TOC
- LSP: Add markdown-toc & markdownlint to Mason ensure_installed
- Plugin: render-markdown.nvim with pretty colors to make Obsidian-esk
  rendering
- Plugin: bullets.nvim for easier bullet-point operations (auto indent,
  auto increment numbers, etc.)
- Chore: Move all markdown plugins to lang-markdown.lua
- Plugin: img-clip.nvim: Paste screenshots from system-clipboard to
markdown (also create store the image as webp)
- Plugin: image.nvim: Show images across neovim. Renders image tags on
markdown

common/.config/nvim/lua/plugins/code-formatting.lua

@@ -17,7 +17,7 @@ return {
                 json = { "prettierd", "prettier", stop_after_first = true },
                 graphql = { "prettierd", "prettier", stop_after_first = true },
                 yaml = { "yamlfmt", "prettierd", stop_after_first = true },
-                markdown = { "markdownlint" },
+                markdown = { "markdownlint", "markdown-toc" },
                 lua = { "stylua" },
                 python = { "black" },
                 sh = { "shfmt", "shellharden", stop_after_first = true },
@@ -53,6 +53,16 @@ return {
                         "~/.config/templates/markdownlint.json",
                     },
                 },
+                ["markdown-toc"] = {
+                    -- Format only if TOC present in the file
+                    condition = function(_, ctx)
+                        for _, line in ipairs(vim.api.nvim_buf_get_lines(ctx.buf, 0, -1, false)) do
+                            if line:find("<!%-%- toc %-%->") then
+                                return true
+                            end
+                        end
+                    end,
+                },
                 yamlfmt = {
                     prepend_args = {
                         "-formatter",