Render horizontal character numbers in `&plain=1`.
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As aforestated at https://github.com/orgs/community/discussions/129450#discussion-6849971:
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When I reference a line, I usually want to reference a specific section of that line, rather than the entire line. However, because horizontal line numbers are not available to utilize text fragment directive instead, as a crude cludge.
An example is https://github.com/PrismLauncher/PrismLauncher/issues/1599#issue-1878841159, where I am forced to cite a text fragment directive appended to the end of a permalink to a line number - https://github.com/PrismLauncher/PrismLauncher/blob/ab68d9198d07674952f99a63bb0901f8a410ce5c/.github/ISSUE_TEMPLATE/bug_report.yml?plain=1#L36:~:text=Help%20%2D%3E%20About%20Prism%20Launcher%20%2D%3E%20About%20Qt - in order to reference a specific *section of a line*.
The 10 upvotes at https://github.com/microsoft/vscode/issues/176174#issue-1610221457, and the existence of https://github.com/Zettlr/Zettlr/issues/163#issue-435417639<!--, https://gitlab.com/gitlab-org/gitlab/-/issues/468550 and https://github.com/microsoft/vscode/issues/216891#issue-2367970547,--> should demonstrate that significant interest exists.
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Unfortunately, this applies to GitLab too (and really, GitLab is what I use more, so it's my focus).
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