chore: remove usage of Str.pad_to method

## Details

Only one usage of `Str.pad_to()` remained after recent checkbox change.
Replace this usage with an equivalent alternative, cleanup the code, and
fix any necessary unit tests.

Author: MeanderingProgrammer

CHANGELOG.md

@@ -15,6 +15,7 @@
   [f9badfb](https://github.com/MeanderingProgrammer/render-markdown.nvim/commit/f9badfb5907a16c8e0d5f3c157d63bcea2aa555e)
 - `code.language_icon` option [#376](https://github.com/MeanderingProgrammer/render-markdown.nvim/issues/376)
   [8ee2701](https://github.com/MeanderingProgrammer/render-markdown.nvim/commit/8ee2701a6c4cdaef7ea0b27c13c26971ae3c9761)
+  [7bf951b](https://github.com/MeanderingProgrammer/render-markdown.nvim/commit/7bf951b8ad93d47b90be290be6fc60da5788ddaa)
 
 ### Bug Fixes
 

lua/render-markdown/health.lua

@@ -5,7 +5,7 @@ local state = require('render-markdown.state')
 local M = {}
 
 ---@private
-M.version = '8.1.12'
+M.version = '8.1.13'
 
 function M.check()
     M.start('version')

lua/render-markdown/lib/str.lua

@@ -45,13 +45,6 @@ function M.pad(n)
     return string.rep(' ', n)
 end
 
----@param target string
----@param s string
----@return string
-function M.pad_to(target, s)
-    return M.pad(M.width(target) - M.width(s))
-end
-
 ---@param s string
 ---@param pattern string
 ---@return Range2[]

lua/render-markdown/render/table.lua

@@ -247,12 +247,12 @@ function Render:delimiter()
         end
     end)
 
-    local text = Str.pad(Str.spaces('start', delim.node.text))
-    text = text .. border[4] .. table.concat(sections, border[5]) .. border[6]
-    text = text .. Str.pad_to(delim.node.text, text)
+    local line = self:append({}, Str.spaces('start', delim.node.text))
+    self:append(line, border[4] .. table.concat(sections, border[5]) .. border[6], self.table.head)
+    self:append(line, Str.width(delim.node.text) - Str.line_width(line))
 
     self.marks:add_over('table_border', delim.node, {
-        virt_text = { { text, self.table.head } },
+        virt_text = line,
         virt_text_pos = 'overlay',
     })
 end

tests/util.lua

@@ -300,10 +300,13 @@ function M.table.delimiter(sections, padding)
         end, widths)
         return table.concat(section, '')
     end, sections)
-    local text = '├' .. table.concat(parts, '┼') .. '┤' .. string.rep(' ', padding or 0)
+    local line = { { '├' .. table.concat(parts, '┼') .. '┤', 'RmTableHead' } }
+    if padding ~= nil then
+        table.insert(line, { string.rep(' ', padding), 'Normal' })
+    end
     ---@type vim.api.keyset.set_extmark
     return {
-        virt_text = { { text, 'RmTableHead' } },
+        virt_text = line,
         virt_text_pos = 'overlay',
     }
 end