Documentation updates (#1032)

* Applying doc changes based on reviews of past several documentation PRs
* Update docs
  Clean up encryption docs
  Clean up security docs
  Delete export.md
  Make new formats.md and add to sidebar. Also add all of the built-in formats, and examples for each.
  Update mkdocs config for new files

* Fix broken docs links
* Correct incomplete sentences and markdown formatting issues
* Make overview a little more concise
* Update some command line arguments to latest version and make it a bit more concise
* Clean up unneeded TOML modifications and other scaffolding not needed for 3.9
* Revert "Clean up unneeded TOML modifications and other scaffolding not needed for 3.9"
  This reverts commit 13b4266ed1.
* Specify that brew is also the easiest way to install jrnl on Linux
* Update docs/security.md
* Update docs/recipes.md
* Doc updates:
- Remove import/export page, fold it into formats
- Rename security to privacy-and-security.md to avoid conflation w/ github security issues
- Various small cleanup and edits from PR review

Co-authored-by: Jonathan Wren <jonathan@nowandwren.com>

docs/encryption.md

@@ -4,26 +4,9 @@
 
 While `jrnl` follows best practices, total security is never possible in the
 real world. There are a number of ways that people can at least partially
-compromise your `jrnl` data. See the [Privacy and Security](./security.md) page
+compromise your `jrnl` data. See the [Privacy and Security](./privacy-and-security.md) page
 for more information.
 
-## Dependencies
-
-As of version 2.0, `jrnl`'s encryption functions require
-[`cryptography`](https://pypi.org/project/cryptography/), which is available in
-the Python Package Index (PyPI) and can be installed using `pip`:
-
-``` sh
-pip3 install cryptography
-```
-
-Previous versions of `jrnl` require
-[`pycrypto`](https://pypi.org/project/pycrypto/):
-
-```sh
-pip3 install pycrypto
-```
-
 ## Encrypting and Decrypting
 
 Existing plain text journal files can be encrypted using the `--encrypt`
@@ -52,7 +35,7 @@ encrypted file untouched and create a new plain text file next to it.
 
 ## Storing Passwords in Your Keychain
 
-There is no method to recover or reset your `jrnl` password. If you lose it,
+Nobody can recover or reset your `jrnl` password. If you lose it,
 your data will be inaccessible forever.
 
 For this reason, when encrypting a journal, `jrnl` asks whether you would like
@@ -66,16 +49,40 @@ same password again. This will trigger the keychain storage prompt.
 
 ## Manual Decryption
 
-Should you ever want to decrypt your journal manually, you can do so with any
-program that supports the AES algorithm in CBC. The key used for encryption is
-the SHA-256 hash of your password. The IV (initialization vector) is stored in
-the first 16 bytes of the encrypted file. The plain text is encoded in UTF-8 and
-padded according to PKCS\#7 before being encrypted.
+The easiest way to decrypt your journal is with `jrnl --decrypt`, but you could
+also decrypt your journal manually if needed. To do this, you can use any
+program that supports the AES algorithm (specifically AES-CBC), and you'll need
+the following relevant information for decryption:
 
-Here is a Python script that you can use to decrypt your journal:
+- **Key:** The key used for encryption is the
+    [SHA-256](https://en.wikipedia.org/wiki/SHA-2) hash of your password.
+- **Initialization vector (IV):** The IV is stored in the first 16 bytes of
+    your encrypted journal file.
+- **The actual text of the journal** (everything after the first 16 bytes in
+    the encrypted journal file) is encoded in
+    [UTF-8](https://en.wikipedia.org/wiki/UTF-8) and padded according to
+    [PKCS\#7](https://en.wikipedia.org/wiki/PKCS_7) before being encrypted.
 
+If you'd like an example of what this might look like in script form, please
+see below for some examples of Python scripts that you could use to manually
+decrypt your journal.
+
+
+
+!!! note
+    These are only examples, and are only here to illustrate that your journal files
+    will still be recoverable even if `jrnl` isn't around anymore. Please use 
+    `jrnl --decrypt` if available.
+
+**Example for jrnl v2 files**:
 ``` python
 #!/usr/bin/env python3
+"""
+Decrypt a jrnl v2 encrypted journal.
+
+Note: the `cryptography` module must be installed (you can do this with
+something like `pip3 install crytography`)
+"""
 
 import base64
 import getpass
@@ -106,11 +113,15 @@ key = base64.urlsafe_b64encode(kdf.derive(password))
 print(Fernet(key).decrypt(ciphertext).decode('utf-8'))
 ```
 
-If you're still using `jrnl` version 1.X, the following script serves the same
-purpose:
-
+**Example for jrnl v1 files**:
 ``` python
 #!/usr/bin/env python3
+"""
+Decrypt a jrnl v1 encrypted journal.
+
+Note: the `pycrypto` module must be installed (you can do this with something
+like `pip3 install pycrypto`)
+"""
 
 import argparse
 from Crypto.Cipher import AES