Add xxtea docs (#4640)

* Add xxtea docs

* Update index.rst

---------

Co-authored-by: Jesse Hills <3060199+jesserockz@users.noreply.github.com>

components/xxtea.rst

@@ -0,0 +1,22 @@
+XXTEA Component
+===============
+
+.. seo::
+    :description: Lightweight encryption algorithm for ESPHome
+    :keywords: xxtea
+
+This component cannot be used directly in YAML, but can be used in lambdas to encrypt and decrypt data.
+
+The encryption used is `XXTEA <https://en.wikipedia.org/wiki/XXTEA>`_ which is fast and compact. XXTEA is known
+to be susceptible to a chosen-plaintext attack, so it should not be used where plain-text injection is possible.
+
+The algorithm has been modified from the original to use a 256 bit key instead of the original 128 bit key.
+
+See the API docs for more information on how to use this component.
+
+See Also
+--------
+
+- :doc:`index`
+- :apiref:`xxtea/xxtea.h`
+- :ghedit:`Edit`

images/xxtea.svg

@@ -0,0 +1 @@
+<svg viewBox="0 0 106 25" id="svg5" xmlns="http://www.w3.org/2000/svg" xmlns:svg="http://www.w3.org/2000/svg"><defs id="defs9"/><path d="M5 0h96a5 5 0 015 5v15a5 5 0 01-5 5H5a5 5 0 01-5-5V5a5 5 0 015-5z" style="fill:#000" id="path2"/><g aria-label="XXTEA" id="component-text" style="font-weight:900;font-size:25px;font-family:Montserrat;letter-spacing:1.1px;fill:#fffffc"><path d="M4.8 21l7.8-10.9L12.575 14.225 5.025 3.5h6.625l4.4 6.5-2.825.025 4.3-6.525h6.35L16.325 14V9.9L24.25 21H17.5l-4.4-6.8 2.725-.025-4.3 6.825z" id="path11"/><path d="m24.949979 21 7.8-10.9-.025 4.125-7.55-10.725h6.625l4.4 6.5-2.825.025 4.3-6.525h6.35l-7.55 10.5V9.9l7.925 11.1h-6.75l-4.4-6.8 2.725-.025-4.3 6.825z" id="path13"/><path d="M49.774938 21V8.075h-5.125V3.5h16.15v4.575h-5.125V21z" id="path15"/><path d="m68.824924 10h7.8v4.25h-7.8zm.4 6.55h8.75V21h-14.55V3.5h14.225v4.45h-8.425z" id="path17"/><path d="m79.449934 21 7.65-17.5h5.8L100.54993 21h-6.099996l-5.65-14.7h2.3l-5.65 14.7zm4.55-3.05 1.5-4.25h8.05l1.5 4.25z" id="path19"/></g></svg>

index.rst

@@ -178,6 +178,7 @@ ESPHome-specific components or components supporting ESPHome device provisioning
     Improv via Serial, components/improv_serial, improv.svg, dark-invert
     Interval, components/interval, description.svg, dark-invert
     JSON, components/json, json.svg, dark-invert
+    XXTEA, components/xxtea, xxtea.svg
     Script, components/script, description.svg, dark-invert
 
 ESPHome Configuration