Extract more info from a git hunk header

Added

• Added GithubDiffParser::Hunk#context which returns the context of the hunk.
  In this example, it would return "def blabla"

  @@ +1,6 -1,18 def blabla

• Added GithubDiffParser::Hunk#previous_line_count which returns the prevous line count in a hunk.
  In this example, it would return 6.

  @@ +1,6 -1,18 def blabla

• Added GithubDiffParser::Hunk#new_line_count which returns the prevous line count in a hunk.
  In this example, it would return 18.

  @@ +1,6 -1,18 def blabla

Fixed

• GithubDiffParser::Diff#previous_line_number_is_now could return a wrong value
  for the line number 1 in a file.

Fix `GithubDiffParser::Diff#new_mode?` and ``GithubDiffParser::Diff#deleted_mode?`

[1.1.1] - 2024-2-21

Fixed

• GithubDiffParser::Diff#new_mode? and ``GithubDiffParser::Diff#deleted_mode?` would raise
  an error with this kind of diff:

  diff --git a/blabla.rb b/app/my_file.rb
  similarity index 100%
  rename from blabla.rb
  rename to app/my_file.rb

Add few convenient methods

[1.1.0] - 2024-2-21

Added

• Github Diff Parser parses the permissions bits and you now have have access to various method
  such as:
  • GithubDiffParser::Diff#normal_file? when the bits are 100644
  • GithubDiffParser::Diff#executable? when the bits are 107555
  • GithubDiffParser::Diff#symlink? when the bits are 120000
• Introduce GithubDiffParser::Diff#symlink_source. When the diff applies to a symbolic link, symlink_source will
  return the path to where the symbolic link points to.
• Introduce GithubDiffParser::Diff#apply, a simple implementation of git apply.
• Introduce GithubDiffParser::Diff#revert, a simple implementation of git apply -R.

Fixed

• GithubDiffParser::Line#content didn't include \n (if the line had one).