Manpages: Auto-generate many through ArgsParser

This set was hand-curated, guided by the questions:
- Does it have at least three options, i.e. is the help page
  non-trivial?
- Is the program unusual, i.e. does listing it in Help or on
  man.serenityos.org spread awareness?
- Is the program common, but we only implement a subset of 'common'
  flags?

Base/usr/share/man/man1/gunzip.md

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+## Name
+
+gunzip
+
+## Synopsis
+
+```sh
+$ gunzip [--keep] [--stdout] <FILE...>
+```
+
+## Options:
+
+* `--help`: Display help message and exit
+* `--version`: Print version
+* `-k`, `--keep`: Keep (don't delete) input files
+* `-c`, `--stdout`: Write to stdout, keep original files unchanged
+
+## Arguments:
+
+* `FILE`: File to decompress
+
+<!-- Auto-generated through ArgsParser -->