[README,#50][s]: add feature checklist in README.

summarized version of job stories in https://datahub.io/notes/markdowndb.

Also added to roadmap epic.

README.md

@@ -9,6 +9,29 @@ MarkdownDB is a javascript library for treating markdown files as a database --
 
 **🚧 MarkdownDB is in its early development stage**
 
+## Features and Roadmap
+
+- [x] **Index a folder of files** - create a db index given a folder of markdown and other files
+  - [ ] BONUS Index multiple folders (with support for configuring e.g. prefixing in some way e.g. i have all my blog files in this separate folder over here)
+  - [x] **Command line tool for indexing**: Create a markdowndb (index) on the command line
+
+Extract structured data like:
+
+- [x] **Frontmatter metadata**: Extract markdown frontmatter and add in a metadata field
+  - [ ] deal with nested frontmatter (? what does this mean?)
+  - [ ] deal with casting types e.g. string, number so that we can query in useful ways e.g. find me all blog posts before date X
+- [ ] **Tags**: Extracts tags in markdown pages
+  - [x] Extract tags in frontmatter
+  - [ ] Extract tags in body like `#abc`
+- [ ] **Links**: links between files like `[hello](abc.md)` or wikilink style `[[xyz]]` so we can compute backlinks or deadlinks etc (see #4)
+- [ ] **Tasks**: extract tasks like this `- [ ] this is a task` (See obsidian data view)
+
+Data enhancement and validation
+
+- [ ] **Computed fields**: add new metadata properties based on existing metadata e.g. a slug field computed from title field; or, adding a title based on the first h1 heading in a doc; or, a type field based on the folder of the file (e.g. these are blog posts). cf https://www.contentlayer.dev/docs/reference/source-files/define-document-type#computedfields. #54
+- [ ] **Data validation and Document Types**: validate metadata against a schema/type so that I know the data in the database is "valid" #55
+  - [ ]  BYOT (bring your own types): i want to create my own types ... so that when i get an object out it is cast to the right typescript type
+
 ## Quick start
 
 ### You have a folder of markdown content