Add missing API's to User guide

[zanzaben]

Describe the bug
In section 8 of the user guide, it lists all the APIs, and some are missing from that list.

cFE Resource ID API's
– CFE_ES_AppID_ToIndex
– CFE_ES_LibID_ToIndex
– CFE_ES_TaskID_ToIndex
– CFE_ES_CounterID_ToIndex

cFE FS File Utility APIs
– CFE_FS_GetDefaultMountPoint
– CFE_FS_GetDefaultExtension
– CFE_FS_ParseInputFileNameEx
– CFE_FS_ParseInputFileName
– CFE_FS_BackgroundFileDumpRequest
– CFE_FS_BackgroundFileDumpIsPending

Expected behavior
Should be listed in section 8.

Additional context
the details of the functions are in there correct place later in the guide.

Reporter Info
Full name and company/organization if applicable