Merge branch 'topic/doc_install' into 'master'

Add `install` target to `doc/Makefile`

See merge request eng/ide/ada_language_server!2004

Author: reznikmm

doc/Makefile

@@ -1,5 +1,9 @@
 # Minimal makefile for Sphinx documentation
 #
+prefix = $(PWD)
+docdir = $(prefix)/share/doc/als
+MKDIR = mkdir -p
+CP = cp -p
 
 # You can set these variables from the command line, and also
 # from the environment for the first two.
@@ -18,3 +22,10 @@ help:
 # "make mode" option.  $(O) is meant as a shortcut for $(SPHINXOPTS).
 %: Makefile
 	@$(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
+
+install:
+	$(MKDIR) $(docdir)/html
+
+	${MKDIR} $(docdir)/html/users_guide/
+	-${CP} -r _build/html/* $(docdir)/html/users_guide/
+