Add format description for BFRI files

src/.vuepress/config.js

@@ -33,6 +33,7 @@ module.exports = {
             'bfmu',
             'bfst',
             'bfum',
+            'bfri',
             'bfwd',
             'bullfrog-library',
             'lips',

src/formats/bfri.md

@@ -0,0 +1,62 @@
+# BFRI (Bullfrog Resource Index)
+
+The BFRI (**B**ull**f**rog **R**esource **I**ndex) file format contains pointers to others Bullfrog string files such as [BF4](/formats/bf4.html), [BFMU](/formats/bfmu.html), [BFST](/formats/bfst.html) and [BFUM](/formats/bfum.html).
+
+## File Format
+
+BFRI files are composed of an global header of 8 bytes, containing the number of files in the index, followed by a list of entries, on for each files.
+Entries are sorted in increasing order for identifier.
+
+### File header
+
+* 4 bytes: Magic number - "BFRI"
+* 4 bytes: File count
+
+### For each file
+
+* 4 bytes: Identifier
+* 2 bytes: File Type
+* 2 bytes: Filename offset
+* 4 bytes: Reserved - a pointer to object used internally
+
+### Identifiers
+
+For each file entry, the identifier can be one of the following:
+
+|  Identifier          | Value   |
+|:---------------------|:-------:|
+| MB2UNICODE           |  0x1    |
+| UNICODE2MB           |  0x2    |
+| ERRORMSG             |  0x3e8  |
+| INGREDIENTS          |  0x3e9  |
+| TAG_SYSTEM           |  0x3ea  |
+| KIDSTATES            |  0x3ec  |
+| STAFFSTATES          |  0x3ed  |
+| UITEXT               |  0x3ee  |
+| UIHELPTEXT           |  0x3ef  |
+| CHAT_COMMANDS        |  0x3f0  |
+| THEMENAMES           |  0x3f1  |
+| OBJECT_NAMES         |  0x3f2  |
+| HANDYMAN_NAMES       |  0x3f3  |
+| MECHANIC_NAMES       |  0x3f4  |
+| ENTERTAINER_NAMES    |  0x3f5  |
+| GUARD_NAMES          |  0x3f6  |
+| RESEARCHER_NAMES     |  0x3f7  |
+| FEMALE_NAMES         |  0x3f8  |
+| ITEMTYPES            |  0x3f9  |
+| LENDER_NAMES         |  0x3fa  |
+| STAFF_TYPES          |  0x3fb  |
+| KEYBOARD             |  0x3fc  |
+
+### File types
+
+File type identify a type of resource and can be one of the following:
+
+| File type                  | Value | Comment                               |
+|----------------------------|-------|---------------------------------------|
+| [BFMU](/formats/bfmu.html) |  0x0  |                                       |
+| BFMH                       |  0x0  | Looks like [BFMU](/formats/bfmu.html) |
+| [BFUM](/formats/bfum.html) |  0x1  |                                       |
+| BFMB                       |  0x2  |                                       |
+| [BFST](/formats/bfst.html) |  0x3  |                                       |
+| [BF4F](/formats/bf4.html)  |  0x4  |                                       |