Yes, it is, the same way third-party component vendors do. As you say, use the free Microsoft Help 2 compiler, Help 2 Workshop, available through MS.
Once you've written and compiled your help, you incorporate it into the IDE's help system via H2Reg.exe, which you can find in your $(BDSDIR)\Help\Doc
folder. Read the comments in h2reg.ini (in that same folder) for details regarding how to do so.