docs: actually link to TortoiseHg in the text

There were no clickable links to thg before.

README.rst

@@ -375,7 +375,7 b' install some missing tool, or library, a'
    Note also, that recent versions of keyring library (since version 12) use Python
    entrypoints to find available backends. Those are incompatible with
    some binary packaging methods (like ``py2app``) and may cause
-   problems. In particular there were packaged installations of TortoiseHG
+   problems. In particular there were packaged installations of TortoiseHG_
    which were unable to load keyring backends. See `#61 <https://foss.heptapod.net/mercurial/mercurial_keyring/issues/61/tortoisehg-encounters-unknown-exception>`_ for some more details.
 
 
@@ -385,7 +385,7 b" Only if this doesn't help, there may be "
 
 By far easiest way to have properly working keyring is to use packaged
 binary version (like ``python-keyring`` Ubuntu package, or keyring
-bundled with TortoiseHG on some systems). If you pip-installed keyring
+bundled with TortoiseHG_ on some systems). If you pip-installed keyring
 and it doesn't work, you may consider removing it via ``pip uninstall
 keyring`` and looking for binary package instead.