Add rule to append text comments

[jeparlefrancais]

Closes #122

This PR adds a new rule that generates a comment at the start or the end of each file. The rule can be configured to take the comment content from the rule configuration or from a file.

For example, to create a comment from the rule configuration itself:

{
  rule: "append_text_comment",
  text: "comment content",
}

Or to create a comment from a file:

{
  rule: "append_text_comment",
  file: "path/to/file.txt",
}

This rule can be configured to append at the start (default) or the end of each file:

{
  rule: "append_text_comment",
  text: "comment content",
  location: "end", // or default is "start"
}

• add rule docs
• add entry to the changelog

[github-actions]

Coverage after merging rule-append-text-comment into main will be

87.20%

Coverage Report for Changed Files

File	Stmts	Branches	Funcs	Lines	Uncovered Lines
src/nodes
block.rs	95.76%	100%	97.70%	95.38%	16, 19, 204–206, 241–246, 25–26, 28, 31, 40, 49–50, 52, 55
identifier.rs	93.88%	100%	90%	94.87%	63–65
src/nodes/expressions
parenthese.rs	79.55%	100%	77.27%	80.30%	100–102, 25–28, 76–78, 99
src/nodes/statements
assign.rs	93.79%	100%	89.66%	94.83%	44–46
function.rs	93.20%	100%	91.43%	93.58%	123–125, 178–179, 181, 38, 383–385, 39, 405, 41, 418, 441–442, 444
generic_for.rs	96.51%	100%	90%	97.89%
if_statement.rs	82.77%	100%	78.33%	83.90%	117, 163, 231–236, 238–240, 242–243, 256–258, 266–269, 27–30, 49–55
last_statement.rs	92.75%	100%	88.57%	94.17%	30–31
local_assign.rs	95.64%	100%	93.10%	96.06%	121–124, 224, 52–53, 55–56
local_function.rs	93.73%	100%	91.38%	94.29%	122–126, 240–242, 272, 285, 311
numeric_for.rs	93.57%	100%	87.10%	95%	163–165, 54
repeat_statement.rs	95.70%	100%	91.30%	97.14%
while_statement.rs	93.81%	100%	86.96%	95.95%
src/rules
append_text_comment.rs	49.37%	100%	62.86%	48.29%	118–125, 141–154, 160–171, 177–186, 192–201, 207–223, 229–240, 246–253, 259–267, 282–300, 321–328, 331–333, 335–337, 347–348, 350–351, 360–362, 366–368, 37, 370–371, 379, 38, 380, 385–389, 39, 390–393, 40, 406–407, 41, 413–419, 42, 420, 43, 450–455, 462, 475, 483–498, 505–507, 54, 56–59, 67, 69–74, 77–81
configuration_error.rs	64.71%	100%	83.33%	61.64%	100, 72–73, 75–77, 79–81, 83–84, 86, 90–99
mod.rs	88.97%	100%	77.78%	90.43%	103–105, 109, 119–121, 139–141, 143, 174–176, 260, 301–302, 337–339, 402–404, 64