Move pages under tldr, lint run.sh, update docs

tldr/linux/add-apt-repository

@@ -0,0 +1,25 @@
+---
+syntax: markdown
+tags: [tldr, linux]
+source: https://github.com/tldr-pages/tldr.git
+---
+# add-apt-repository
+
+> Manages `apt` repository definitions.
+> More information: <https://manned.org/apt-add-repository>.
+
+- Add a new `apt` repository:
+
+`add-apt-repository {{repository_spec}}`
+
+- Remove an `apt` repository:
+
+`add-apt-repository --remove {{repository_spec}}`
+
+- Update the package cache after adding a repository:
+
+`add-apt-repository --update {{repository_spec}}`
+
+- Allow source packages to be downloaded from the repository:
+
+`add-apt-repository --enable-source {{repository_spec}}`