yadm: add pages (#13920)

Co-authored-by: Sebastiaan Speck <12570668+sebastiaanspeck@users.noreply.github.com>
Co-authored-by: Wiktor Perskawiec <git@spageektti.cc>

pages/common/yadm-bootstrap.md

@@ -0,0 +1,9 @@
+# yadm-bootstrap
+
+> Execute Yadm's bootstrap file.
+> This file should be created in `$HOME/.config/yadm/bootstrap`.
+> More information: <https://yadm.io/docs/bootstrap>.
+
+- Execute bootstrap executable:
+
+`yadm bootstrap`