gitk: add README with usage, build, and contribution details

Signed-off-by: Michael Rappazzo <rappazzo@gmail.com>
Signed-off-by: Johannes Sixt <j6t@kdbg.org>

README.md

@@ -0,0 +1,93 @@
+Gitk - The Git Repository Browser
+=================================
+
+Gitk is a graphical Git repository browser. It displays the commit
+history of a Git repository as a graph, showing the relationships
+between commits, branches, and tags.
+
+Usage
+=====
+
+To view the history of the current repository:
+```bash
+gitk
+```
+
+To view the history of specific files or directories:
+```bash
+gitk path/to/file
+gitk path/to/directory
+```
+
+To view a specific branch or range of commits:
+```bash
+gitk branch-name
+gitk v1.0..v2.0
+```
+
+For more usage examples and options, see the [gitk manual](https://git-scm.com/docs/gitk).
+
+Building
+========
+
+Gitk is a Tcl/Tk application. It requires Tcl/Tk to be installed on
+your system.
+
+Running directly
+----------------
+
+Gitk can be run from the source directory without installation:
+
+```bash
+./gitk
+```
+
+This allows for quick testing of changes.
+
+Installation
+------------
+
+To install system-wide, you can use either `make` or `meson`:
+
+```bash
+# Install to default location ($HOME/bin)
+make install
+
+# Install to system-wide location
+sudo make install prefix=/usr/local
+
+# Install to custom location
+make install prefix=/opt/gitk
+
+# Using Meson
+meson setup builddir
+meson compile -C builddir
+meson install -C builddir
+```
+
+Both build systems will handle setting the correct Tcl/Tk interpreter
+path and installing translation files.
+
+Contributing
+============
+
+Contributions are welcome! The preferred method for submitting patches
+is via email to the Git mailing list, as this allows for more thorough
+review and broader community feedback. However, GitHub pull requests
+are also accepted.
+
+All commits must be signed off (use `git commit --signoff`) and should
+have commit messages prefixed with `gitk:`.
+
+Email Patches
+-------------
+
+Send patches to git@vger.kernel.org and CC j6t@kdbg.org. See the Git
+project's [patch submission guidelines](https://git-scm.com/docs/SubmittingPatches)
+for detailed instructions on creating and sending patches.
+
+License
+=======
+
+Gitk is distributed under the GNU General Public License, either
+version 2, or (at your option) any later version.