qtgrace: add page (tldr-pages#22518)

Co-authored-by: Magrid <magrid0@proton.me>
Co-authored-by: Ivan Baluta <ivanbaluta.dev@gmail.com>
Co-authored-by: Lena Pastwa <lena@lnps.me>

Author: 4 people

pages/linux/qtgrace.md

@@ -0,0 +1,25 @@
+# qtgrace
+
+> Display, plot, analyze 2D data.
+> A Qt reimplementation of Grace (<https://plasma-gate.weizmann.ac.il/Grace/>), sharing its command-line interface.
+> More information: <https://sourceforge.net/projects/qtgrace/>.
+
+- Plot one or more data files, plotting only the first two columns in each file as X Y:
+
+`qtgrace {{path/to/file1.dat path/to/file2.dat ...}}`
+
+- Plot one or more data files, plotting all columns in each file as X Y1 Y2 ...:
+
+`qtgrace {{-nxy path/to/file1.dat -nxy path/to/file2.dat ...}}`
+
+- Plot one or more data files with a logarithmically scaled x-axis:
+
+`qtgrace -log x {{path/to/file1.dat path/to/file2.dat ...}}`
+
+- Plot a data file with a logarithmic scale on both axes, with data formatted as X Y DY:
+
+`qtgrace -log xy -settype xydy {{path/to/file.dat}}`
+
+- Display help:
+
+`qtgrace -help`