fix: account for columns before text when getting window width

## Details

The current window width gets the entire available space for a window,
but not the usable space. This was okay for getting a fill width but is
not great when computing offsets to center blocks.

The fix is to use the `getwininfo` `textoff` property which conveniently
tells us the width of foldcolumn, signcolumn and numbers before text,
exactly what we're looking for.

To avoid re-computing this cache the value after it is first accessed so
we can re-use it within the same parse cycle.

Author: MeanderingProgrammer

Diff for: CHANGELOG.md

@@ -11,6 +11,7 @@
 - pad setext header lines [75a0a95](https://github.com/MeanderingProgrammer/render-markdown.nvim/commit/75a0a9596a91130fae43d3b7c0d6c651645ef1df)
 - center headings and code blocks [#179](https://github.com/MeanderingProgrammer/render-markdown.nvim/issues/179)
   [0986638](https://github.com/MeanderingProgrammer/render-markdown.nvim/commit/0986638b381a4b01eb108bb946f3a67a9eb3d0ec)
+- integrate with lazy.nvim filetypes [cb9a5e2](https://github.com/MeanderingProgrammer/render-markdown.nvim/commit/cb9a5e2412d21c7a89627e0d6da5459acbc0eb9c)
 
 ### Bug Fixes
 

Diff for: lua/render-markdown/core/context.lua

@@ -11,6 +11,7 @@ local util = require('render-markdown.core.util')
 ---@field private components table<integer, render.md.CustomComponent>
 ---@field private conceal? table<integer, [integer, integer][]>
 ---@field private links table<integer, [integer, integer, integer][]>
+---@field private window_width? integer
 ---@field last_heading integer
 local Context = {}
 Context.__index = Context
@@ -29,6 +30,7 @@ function Context.new(buf, win, offset)
     self.components = {}
     self.conceal = nil
     self.links = {}
+    self.window_width = nil
     self.last_heading = -1
     return self
 end
@@ -112,7 +114,14 @@ end
 
 ---@return integer
 function Context:get_width()
-    return vim.api.nvim_win_get_width(self.win)
+    if self.window_width == nil then
+        self.window_width = vim.api.nvim_win_get_width(self.win)
+        local window_info = vim.fn.getwininfo(self.win)
+        if #window_info == 1 then
+            self.window_width = self.window_width - window_info[1].textoff
+        end
+    end
+    return self.window_width
 end
 
 ---@param other render.md.Context

Diff for: lua/render-markdown/health.lua

@@ -4,7 +4,7 @@ local state = require('render-markdown.state')
 local M = {}
 
 ---@private
-M.version = '7.1.8'
+M.version = '7.1.9'
 
 function M.check()
     M.start('version')